Use of diels-alder adducts as tobacco additives

United States Patent Office _Pate„_ted

047,433

USE OF DIELS-ALDER ADDUCTS AS TOBACCO ADDITIVES

Abraham Bavley, Bon Aire, and Ernest W. Robb Π, Richmond, Va., assignors to Philip Morris Incorporated, New York, N.Y., a corporation of Virginia

No Drawing. Filed Oct. 19, 1961, Ser. No. 146,372

Claims. (Cl. 131—17)

This invention relates to tobacco compositions and to methods for their preparation. More particularly, the present invention relates to tobacco compositions containing additives which improve the aroma and flavor characteristics of the tobacco. The invention also relates to methods for the preparation of said additives and for their incorporation in tobacco compositions.

Tobacco compositions usually contain a blend of various tobaccos. In addition, they also generally contain additives, such as flavorants, plasticizers and the like, which impart additional desirable properties to the tobacco compositions.

In the case of additives which are employed commercially to incorporate flavors into tobacco products, many difficulties have been encountered.

A commonly employed method consists of introducing the flavoring additive directly onto the tobacco. Menthol and most natural flavoring extracts are now added to tobacco in this manner. This method has several disadvantages. In the first place, many of the more desirable organic flavor additives are volatile at normal room temperatures or at temperatures higher than normal room temperatures which may be encountered during, the processing of the tobacco. In such event, these flavors are lost during storage of the tobacco products in which they have been incorporated or are lost during processing steps which occur after they have been incorporated in the tobacco composition. In the second place, the flavor additives are generally desired to provide their effect in the tobacco smoke and they often contribute undesirable odors to the aroma of the tobacco product before it is smoked. For example, a flavorant may impart an undesirable odor to a pack of cigarettes, when its purpose is to provide an odor that is desired in the cigarette smoke. In the third place, some additives may also volatilize ahead of the burning area of tobacco, during the smoking of the tobacco product in which they are incorporated. In such a case, their transfer to the aerosol phase of smoke is inefficient and not subject to sufficient control, with regard to the amount of flavor which is imparted to the smoke.

Another method which has been tried for the introduction of flavors in tobacco compositions is the use of the so-called' encapsulated flavors. These are flavors which have been dispersed in gums to prevent them from volatilizing. However, in addition to the higher expenses and additional operations involved in their use, these encapsulated flavors also suffer from certain disadvantages. In the first place, the high moisture content of tobacco is often sufficient to dissolve the capsules and to release the flavors prematurely. Secondly, the pyrolysis product of the encapsulating agent may impart an undesirable odor to the smoke. Such pyrolysis products may even produce noxious flavors and unhealthy effects which are transmitted in the smoke.

The present invention overcomes all of the abovementioned disadvantages of the prior art. The invention provides novel compositions and a novel method for incorporating an extremely wide variety of flavor additives in tobacco compositions, by a manner in which:

(a) The flavors and aromas are not lost due to volatilization during storage of the tobacco product or, during smoking, due to volatilization in an area ahead of the burning area of the tobacco;

(b) The aromas are not released during storage and thus do not contribute any flavor or aroma to the tobacco 5 product which might be undesired prior to the smoking of the tobacco; and (c) No undesirable odors or qualities are imparted to the smoke, such as might be produced by the burning of a gel capsule.

In accordance with the present invention, flavorants are incorporated into tobacco products in the form of Diels-Alder adducts or their salts, the flavorants being the diene and/or dienophile, as will be more fully explained in the remainder of this specification. These flavor-containing Diels-Alder adducts or their salts are non-volatile and stable under the conditions which exist during processing and storage of the tobacco product so that the flavors are maintained and preserved. The flavors and aromas are released only upon smoking of the tobacco composition, whereby the Diels-Alder adduct or its salt is broken down by the heat into the flavorant, which is almost always the starting diene and dienophile but may also be other break-down products of the adduct which are flavorants, which then volatilizes into the smoke 23 stream.

The non-volatile, flavor-containing Diels-Alder adducts which can be employed in accordance with the present invention include in their structures six-membered hydroaromatic rings and can be prepared in accordance with ³⁰ procedures which are well known in the art. For example, the reactions may be conducted in accordance with the teaching of Kloetzel on pages 1-60 of “Organic Reactions,” volume 4, John Wiley and Son, Inc. (1948) or the teachings of Holmes on pages 60-174 of the same ³⁵ volume. In these procedures two reactants are employed:

(1) a conjugated diene and (2) a dienophile.

In the process as employed in the present invention, at least one of the two reactants is a flavorant and the other reactant is either an innocuous non-flavorant or a second flavorant.

The reaction between the diene and the dienophile 45 generally takes place in accordance with one of the following four types of reactions, which are schematically presented below merely for purposes of illustration:

Diene Dienophile Adduct

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3,047,433

Diene Dienophile Adduct

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Compounds which can be employed as the conjugated dienes include conjugated systems of the following types:

(1) Acyclic conpugates, such as butadiene, alkylbutadienes, e.g. isoprene, arylbutadienes, and conjugated polyenes. Specific examples of such acyclic compounds include:

Butadiene,

Trans-l,3-pentadiene (trans-piperylene), Trans-piperylene,

Piperylene,

2-methyl-1,3-butadiene (isoprene),

Isoprene,

1,3-hexadiene,

2,4-hexadiene,

2-methyl-l, 3 -pentadiene, 3 -methyl-1,3 -pentadiene, 4-methyl-1,3 -pentadiene, 2,3 -dimethyl-1,3 -butadiene, 2,3 -dimethyl-1,3 -butadiene, 2,4-heptadiene,

5-methyl-1,3 -hexadiene, 3-methyl-2,4-hexadiene, 2,4-dimethyl-l ,3-pentadiene, 4-ethyl-l,3-hexadiene, 2-cyclopropyl-1,3-butadiene, 2,6-dimethyl-3,5-octadiene, 7-methyl-3-methylene-l,6-octadiene (myrcene), 5-methyl-4-isopropyl-l,3-hexadiene,

-phenyl-1,3 -but adiene, 4-phenyl-l,3-pentadiene, 1-(3 ',4'-methylenedioxyphenyl) -1,3-butadiene, 2-methyl-1 -phenyl-1,3 -butadiene, 6-phenyl-l,3-hexadiene, 4-p-tolyl-l,3-pentadiene, l-(3',4'-dimethoxyphenyl)-l,3-butadiene, 4- (2',4'-dimethylphenyl) -1,3-pentadiene, l-butadienyl-2-vinyl-3-cyclohexene,

-a-naphthyl-1,3 -butadiene,

3-tert-buty 1-1-phenyl-1,3-butadiene, Trans-trans-l,4-diphenyl-l,3-butadiene, 1,4-diphenyl-l,3-butadiene, 2,3 -diphenyl-1,3 -butadiene,

1,2-diphenyl-1,3-pentadiene,

1,2,4-triphenyl-1,3-butadiene, l-p-biphenyl-4-phenyl-l,3-butadiene, 2,3-dimethoxy-l,3-butadiene, 2-(3-methyl-l,3-butadienyl) methyl thioether, 2-(3-methyl-l,3-butadienyl) ethyl thioether, 2-(3-methyl-l,3-butadienyl) n-propyl thioether, 2-(3-methyl-l,3-butadienyl) isopropyl thioether, 2-(3-methyl-l,3-butadienyl) tert-butyl thioether, 2-(3-methyl-l,3-butadienyl) phenyl thioether, 2-formoxy-1,3 -butadiene (formoprene), 2-acetoxy-1,3 -butadiene cis-1,3,5-hexatriene, Trans-l,3,5-hexatriene,

1,3,5-hexatriene,

2,5-dimethyl-1,3,5-hexatriene,

2,6-dimethyl-2,4,6-octatriene (allo-ocimene), Allo-ocimene,

4-phenyl-1,3,6-hept atriene,

4-o-tolyl-l,3,6-heptatriene, l-(2',6',6'-trimethylcyclohexenyl)-3-methyl-l,3-butadiene,

2-methyIenedicyclohexylideneethane, 1,6-diphenyl-1,3,5 -hexatriene,

Alpha-( l-delta¹-octahydronaphthyl) -beta-(2'-methylenecyclohexylidene) -ethane,

Calciferol acetate,

1,8-diphenyl-1,3,5,7-octatetraene,

Vitamin A,

Acetyl vitamin A, Benzoyl vitamin A, Biosterol, Biosteryl acetate, Biosteryl palmitate, 1,10-diphenyl-1,3,5,7,9-decapentaene, Carotene, Sorbic acid, Ethyl sorbate,

Ethyl trans-trans-muconate, 9,11-octadecadienoic acid, Ethyl 9,11-octadecadienoate, 9,11,13-octadecatrienoic acid (alpha-eleostearic acid), Alpha-eleostearic acid, Beta-eleostearic acid, Beta-eleostearin, 4-keto-9,l'l,13-octadecatrienoic acid (alpha-licanic acid), Alpha-licanic acid, Beta-licanic acid, l,3-hexadien-5-yne, 2,5-dimethyl-l,5-hexadien-3-yne.

Acyclic compounds which are particularly useful as flavorants for use in this invention include:

Butadiene,

Trans-1,3-pentadiene (trans-piperylene), 2-methyl-l,3-butadiene (isoprene), 1,3-hexadiene, 2,4-hexadiene, 2-methyl-1,3 -pentadiene, 3 -methyl-1,3 -pentadiene, 4-methyl-l,3-pentadiene, 2,3-dimethyl-l, 3-butadiene, 2,4-heptadiene, 5-methyl-l ,3 -hexadiene, 3-methyl-2,4-hexadiene, 2,4-dimethyl-l,3-pentadiene, 4-ethyl-l,3-hexadiene, 2,6-dimethyl-3,5-octadiene, 7-methyl-3-methylene-l,6-octadiene (myrcene), 5-methyl-4-isopropyl-1,3 -hexadiene, 2-acetoxy-1,3-butadiene, Cis-l,3,5-hexatriene,

Trans-1,3,5-hexatriene, 2,5-dimethyl-1,3,5 -hexatriene, 2,6-dimethyl-2,4,6-octatriene (allo-ocimene), Ocimene, Sorbic acid, Ethyl sorbate.

(2) Alicyclic conjugates, including— (a) Wholly alicyclic systems, such as cyclopentadiene, 1,3-cyclohexadiene, fulvenes, alpha-phellandrene and alpha-terpinene;

(6) Bicyclic systems, such as 1,1'-bicyclohexenyl;

(c) Alicyclic-acyclic systems, such as 1-vinyl-cyclohexene and l-vinyl-3,4-dihydronaphthalene.

Specific examples of such alicyclic compounds include:

Cyclopentadiene,

1,5,5-trimethyl-l ,3 -cyclopentadiene, 1 -benzyl-1,3 -cyclopentadiene, 2-benzyl-l,3-cyclopentadiene,

1,4-diphenyl-l,3-cyclopentadiene, l-phenyl-4-p-tolyl-l,3-cyclopentadiene, 6,6-dimethylfulvene,

6,6-pentamethylenefulvene, 6-styrylfulvene,

6,6-diphenylfuIvcne, l-carbomethoxy-.l,3-cyclopentadiene, 1 - carbomethoxy - 4,5,5 - trimethyl - 1,3 - cyclopentadiene (methyl alpha-camphylate),

- carbomethoxy - 1,5,5 - trimethyl - 1,3 - cyclopentadiene (methyl beta-camphylate),

Pentaphenylcyclopentadienol,

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2,5-dimethyl-3,4-diphenyl-l,3-cyclopentadienone, 3,4-diphenyl-l,3-cyclopentadienone, Tetraphenylcyclopentadienone (tetracyclone), Tetracyclone,

2,5 - diphenyl - 3,4 - (o,o' - biphenylene) - 1,3 - cyclopentadienone (phencyclone),

2,5 - diphenyl - 3,4 - (l',8' - naphthylene) - 1,3 - cyclopentadienone (acecyclone),

Acecyclone, 3a,7a-dihydro-₃,3a,5,6-tctraphenylmden-l-one, 1,3 -cyclohexadiene, 1,3,5,5-te tram ethyl-1,3 -cyclohexadiene, l,5,5,6-tetramethyl-l,3-cyclohexadiene (alpha-pyronene), Alpha-pyronene, l,2,6,6-tetramethyl-l,3-cyclohexadiene (beta pyronene), Beta-pyronene, l-5-isopropyl-l,3-cyclohexadiene, d-Alpha-phellandrene, 1 -alpha-phellandrene, Alpha-phellandrene, 1-beta-phellandrene, Menogene, Alpha-terpinene (1,3-menthadiene), Alpha-terpinene, 3,5-diethoxy-l,6-dihydrophthalic anhydride, 4,5-diphenyl-l,2-dihydrophithalic acid, Levopimaric acid, Abietic acid, Methyl abietate, Rosin, Ergosterol acetate, 22,23-dihydroergosterol acetate, Dehydroergosterol acetate, 7-dehydrochloesterol acetate, Iso-dehydrochlosterol acetate, 7-dehydrositosterol acetate, Ergosterol-B₃ acetate, Pyrocalciferol, Isopryrovitamin D, Lumisterol acetate, 1,3 -cycloheptadiene, Cycloheptatriene, Eucarvone, 1,1 '-bicyclopentenyl, 1,1 '-bicyclohexenyl, 3,4,3 '4'-tetrahydro-1,1 '-binaphthyl, 3,4,3 ',4'-tetrahydro-2,2'-binapihithyl, 3,4,3',4'-tetrahydro-7,7'-dimethyl-l,l'-binaphthyl, 3,3'-biindenyl, 1 -vinyl-1 -cyclohexene, 2-methyl-1 -vinyl- 1-cyclohexene, 1 -vinyl-3,4-dihydronaphthalene, 1 -vinyl-6-methoxy-3,4-dihydronaphthalene, l-ethynyl-6-methoxy-3,4-dihydronaphthalene, 2 - acetoxy - 10 - methyl - 8 - vinyl - 5,8,9,10 - tetrahydro1,4-naphthoquinone, 1-cyclopentenyliso-propenylacetylene, 1 -cyclohexenyl-1 '-cyclopentenylacetylene, Di-1 -cyclohexeny lacetylene, 2-metihyl-di-l-cyclohexenylacetylene.

Alicyclic compounds which are particularly useful as flavorants for use in this invention include:

Cyclopentadiene,

1,5,5-trimethylcyclopentadiene, l-carbomethoxy-l,3-cyclopentadiene,

- carbomethoxy - 4,5,5 - trimethyl - 1,3 - cyclopentadiene (methyl «,-camphylate),

- carbomethoxyl - 1,5,5 - trimethyl - 1,3 - cyclopentadiene (methyl |8-camphylate),

1,3 -cyclohexadiene,

1,3,5,5-tetramethyl-1,3-cyclohexadiene, l,5,5,6-tetramethyl-l,3-cyclohexadiene, l,5,5,6-tetramethyl-l,3-cyclohexadiene (α-pyronene), 1,2,6,6-tetramethy 1-1,3 -cyclohexadiene (/3-pyronene ),

-5 -isopropyl-1,3-cyclohexadiene, d-a-phellandrene, 1-a-phellandrene, l-p-phellandrenc, α-terpinene (1,3-menthadiene),

1,3-cyclcheptadiene,

Cycloheptatriene,

Eucarvone,

1, P-bicy clopentenyl,

1,1’-bicyclohexenyl,

1-vinyl-1 -cyclohexene,

2-methyl-1 -vinyl- 1-cyclohexene.

(3) Aromatic conjugates, including— (a) Wholly aromatic systems, such as antracene, 9,10¹³ dialkyl-anthnacenes and pentacenes;

(b) Aromatic-acyclic systems, such as isosafrole, 1vinylnaphthalene, and 9-vinyl phenanthrene;

(c) Aromatic-alicyclic systems, such as 1-alpha naphthyl- 1 -cyclop entene.

²θ Specific examples of aromatic compounds include:

Anthracene,

9-methylanthracene,

2-isopropenylanthracene,

9-phenylanthracene, 9-benzylanthracene, 9-acetoxyanthracene, 9,10-dimethylanthracene, 9,10-anthracenedipropionic acid,

9,10-anthacenedi-n-butyric acid,

9,10-dimethoxyanthracene, Anethole, Isosafrole, Isocugenol methyl ether, 35 cis-Isoeugenol ethyl ether,

2,3-dimethoxy-l-propenyl-benzene, 1-(3 ',4'-methylenedioxyphenyl) -1 -pentene, Methyl-3,4-methylenedioxyphenyl-acetylene (piperonylallylene), as-Diphenylethylene„ Indene,

1-vinylnaphthalene, 2-vinylnaphthalene, 1,-propenylnaphthalene, 1 -vinyl-6-methoxynaphtlialene, 1-( analpha-naphthyl )-1 -cyclopentene, 1 - (beta-naphthyl )-1 -cy olopentene, 2-methyl-1- (alpha-naphthyl) -1 -cyclopentene, 2-methyl-1- (beta-naphthyl) -1 -cyclopentene,

1- (6'-methoxy-2'-naphthyl )-1 -cyclopentene,

- (6'-methoxy-2'-naphthy 1) -2-methyl-l -cyclopentene,

- (beta-naphthyl) -1 -cyclohexene.

Aromatic compounds which are particularly useful as flavorants for use in this invention include:

Anethole, isosafrole, isoeugenol methyl ether, cis-isoeugenol ethyl ether, 2,3-dimethoxy-l-propenyl benzene, 1-(3¹,4¹-methylene-dioxyphenyl) -1 -pentene, methyl-3,4methylenedioxyphenyl-acetylene (piperonyl-allylene).

(4) Heterocyclic compounds, such as furan, isobenzo⁶⁰ furans and alpha-pyrone.

Specific examples of heterocyclic compounds include:

Furan,

2-methylfuran (sylvan),

2-ethylfuran,

2- (beta-phenylethyl) -furan,

2- (beta-m-methoxyphenylethyl) -furan, 2-vinylfuran,

Furfurylacetone,

3-hydroxyfuran, Furfuryl acetate, Furfural diacetate, Furfuryl methyl ether, 2,5-dimethylfuran,

2-methyl-5-isopropylfuran,

3,047,433

2-sec-butyl-5 -methylfuran, 5-methylfurfurylacetophenone, 5-methyIfurfuryIacetop!ienone, 2,5-bis- (gamma-ketobutyl) -furan, Beta-(5-methyl-2-furyl)-n-butyraldehyde, 1,3-diphenylisobenzofuran, 1,3-di-p-tolylisobenzofuran, 1,3-diphenyl-4,7 -dimeth ylisobenzofuran, l,3-diphenyl-5,6-dimethylisobenzofuran, l,3-di-p-tolyl-5,6-dimethylisobenzofuran, 1,3-di-alpha-naphthylisobenzofiiraii, l-benzoyl-3-phenylisobenzofuran, 2,6-dimethyl-3-propenyl-5,6-dihydro-l,2-pyran, Alpha-pyrone (coumalin), Coumalin, 5-methyl-alpha-pyrone, 5-ethyl-alpha-pyrone, 4,6-dimethyl-alpha-pyrone,

Alpha-pyrone-5-carboxylic acid (coumalic acid), Methyl coumalate, 4,6-dimethyl-alpha-pyrone-5-carboxylic acid (isohydroacetic acid).

Heterocyclic compounds which are particularly useful as flavorants for use in this invention include:

Furan, 2-methylfuran (sylvan), 2-ethylfuran, 2-vinylfuran, Furfurylacetone, 3-hydroxyfuran, Furfuryl acetate, Furfuryl methyl ether, 2,5 -dimcthylf uran, 2-methyl-5 -isopropylfuran, 2-sec-butyl-5-methylfuran, 5-methylfurfurylacetone, 2,5-bis-(7-ketobutyl)-furan, /3-(5-methyl-2-furyl)-n-butyraldehyde, 2,6-dimethyl-3 -propenyl-5,6-dihydro-1,2-pyran, a-pyrone (coumalin), 5-methyl-a-pyrone, 5-ethyl-a-pyrone, 4,6-dimethyl-a-pyrone, Methyl coumalate.

Compounds which can be employed as the dienophiles contain a 0=0 bond which is conjugated with a C=C, although compounds with a bond which is equivalent in its effect to 0=0 may also be employed.

These compounds generally fall into the following categories:

(1) CH₂=CHA wherein A=CHO, COOH, COOCH₃, COOC₂H₅, COCI, COCH₃, COCeH₅, CN, N0₂, C_eH_g, CH₂0H, CH₂X, CH₂NH₂, CH₂, CN, CH₂COO₂H, CH₂NCS, OCOCHs, SC₆H₄CH₃, SOjR, X, H.

(2) C₆H₅CH=CHA wherein A=CHO, COOH, COOCHg, COOC₂H₆, COCH_s, COC₆H₅.

(3) CH₂=CA₂ wherein A=COOC₂H₅, CN, COCH₃, X.

(4) ACH=CHA wherein A=COOH, COCI, COOCH₃, COOC₂H₅, COCH_3j COC₆H₅, X.

(5) Quinones.

(6) AC=CA wherein A=COOH, COOCH₃,

COOC₂H₅, COC₆H₅, H

Specific examples of such dienophiles include: acrolein, crotonaldehyde, cinnamaldehyde, acetylethylene (methyl vinyl hetone) ethylidene acetone, vinyl phenyl hetone, benzal acetone, benzalacetophenone, debenzal acetone, 1cyclopenten-2-one and its derivatives, l-cyclohexen-3-one, diacetylethylene, diaroylethylenes, acrylic acids, crotonic acid, crotonyl chloride, cinnamic acids and esters, 3,4dehydro-l-naphthoic acids and esters, coumarin, betaaroyl acrylic 'acids, alkylidene-malonic, and acetoacetic esters, ethylene tetra-carboxylic acid and ester, azodicarboxylic ester, acrylonitrile, cyclopentadiene, 1,3 cyclo hexadiene, styrene, indenes, acenaphthalene, allyl compounds, vinyl esters and ethers, 4-vinyl-l-cyclohexene, 1methyl-l-cyclopentene, unsaturated bicyclic compounds, such as dicyclopentadiene and ethylene.

Preferred compounds for use as dienophiles include maleic anhydride and other closely related dicarboxylic acid derivatives, alpha, beta-unsaturated carbonyl compounds, acetylenic compounds, quinones and cyclic ketones.

Particularly suitable dienophiles for use as flavorants in accordance with this invention include:

(a) Such alpha,beta-unsaturated aldehydes as cinnamic aldehyde, alpha-alkyl cinnamic aldehydes, cyclopenten-1al and cyclohexene-l-al.

(Z>) Such alpha,beta-unsaturated acids, esters, and carboxylic acid derivatives as maleic acid, maleic anhydride, dimethyl maleate, diethyl maleate, dimethyl fumarate, diethyl fumarate, citraconic anhydride, itaconic anhydride, cinnamic acid, 3,4-dimethoxycinnamic aldehyde, methyl cinnamate and ethyl cinnamate, coumarin.

(c) Such alpha,beta-unsaturated ketones as cyclopentenone, cyclohexenone and benzalacetone.

(d) Such allyl compounds as allyl alcohol, allyl methyl ether, allyl ethyl ether.

(e) Such acetylenic compounds as acetylene dicarboxylic acid, propiolic acid, acetylene.

(/) Such vinyl compounds as ethylene, vinyl formate, vinyl acetate, vinyl stearate, vinyl acetic acid, vinyl ethyl ether, vinyl methyl ether, vinyl butyl ether, styrene, anethole.

The diene and dienophile may be reacted to form the Diels-Alder adduct, either in the absence or in the presence of a solvent. Suitable solvents include water, and organic solvents, either aqueous or anhydrous, such as benzene, dioxane, xylene, nitrobenzene, acetone, chlorobenzene, ethyl ether, toluene, cyclohexane, o-dichlorobenzene, acetic acid, acetic anhydride, propionic acid and ligroin.

The temperature of the reaction may vary between wide limits, for example from 0° C. to 250° C. The time of the reaction may also vary over wide limits, for example, it may be between about 5 minutes and several days.

As described earlier in this specification, at least one of the Diels-Alder reactants, either the diene or the dienophile, should be a flavorant. By “flavorant,” as used throughout this specification, is meant a material which will volatilize under the conditions of pyrolysis existing when tobacco is burned and which imparts a desired flavor to the tobacco smoke when it is present therein.

The other Diels-Alder reactant may also be a flavorant or it may be an innocuous material which either remains in the ash in an inactive condition, imparting no flavor to the smoke, or volatilizes to form an innocuous gas which imparts no flavor to the smoke.

While the Diels-Alder adducts described above may be employed per se in tobacco compositions, their salts are also useful adducts. The sodium salt is the most preferred salt, but other salts such as potassium, calcium, barium, lithium, aluminum, magnesium or other non-toxic salts, may also be employed. Such salts may be prepared by reacting the adduct with the hydroxide or other base, such as the carbonate or bicarbonate of the metal desired. For example, the adduct is reacted at 0° to 100° C. preferably at room temperature, with a sodium hydroxide solution, containing 0.5 to 1.5 mols of sodium hydroxide. The resulting solution is then evaporated to yield the sodium salt.

The Diels-Alder adducts or their salts can be added to tobacco in a range of .05 to 5% by weight of the total tobacco composition, depending upon the amount of volatile flavorant which is desired in the smoke.

The following examples are illustrative:

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Example 1

Anethole and maleic anhydride were reacted according to the procedure of Cookson and Wariyar, J. Chem. Soc., 1956, 2302. The adduct, 6.57 g., in 50 ml. of water was stirred at room temperature while 2 N sodium hy- ⁰droxide was added dropwise until a permanent pink color with phenolphthalein was observed. 38.2 ml. of sodium hydroxide was required. Evaporation of the resulting solution gave the tetra-sodium salt as an odorless, hygroscopic solid which did not melt below 320°. ⁴⁰

The tetrasodium salt, 0.20 g., was heated to 750° C.

in a stainless steel needle for 60 seconds. During the heating, 500 ml. of air was drawn through the needle and then through a Cambridge filter. The filter was extracted first with 10 ml. of ether, then with 25 ml. of ⁴⁵water. Gas chromatography of the ether extract on a 2 meter Col. R column at 190° C. showed 9.1 mg. of anethole in the extract. No other components were present. The residues from evaporation of the aqueous and ethereal extracts were examined separately by paper ²⁰chromatography, using Whatman 3MM paper and an ether-formic acid-water (5:2:1) solvent system. No maleic acid or other acids were detected. Chromatography of known acids in this system showed that as little as 20 micrograms of acid could have been detected. Any maleic anhydride present would have been converted to maleic acid and identified as such under the conditions used.

A solution of .112 g. of the tetrasodium salt in 2.0 ml. of water was sprayed uniformly on to 10 g. of tobacco ³θ (Philip Morris uncased filler). The tobacco was made into cigarettes, which were evaluated by subjective smoking procedures. It was found that the cigarettes had a pleasing anise flavor. Anethole could be detected in the _ smoke by gas chromatographic technique. '^J'^j

Example 2

Menthofuran, 1.0 g., in 3.0 ml. of benzene was treated with 1.0 g. of maleic anhydride. After 3 hours the crystalline adduct was filtered off and recrystallized from ben- ⁴⁰zene, giving 0.52 g. of the adduct, M.P. 133.5-134.0° C. The adduct was converted to the disodium salt by suspending it in 25 ml. of water, adding 20 ml. of 0.2 ml. of 0.2 N sodium hydroxide, and stirring the mixture for 4 hours. Evaporation of the resulting solution gave the 45 salt as an odorless, white solid which did not melt below 320° C.

The disodium salt, 0.10 g., was pyrolyzed at 750° C. by the method described in Example 1, and the products examined in the same manner. 8.2 mg. of menthofuran, observed by gas chromatography (Col. R, 150° C.) was the only volatile product. No maleic acid was found in the aqueous or ethereal extracts of the pyrolysate.

A solution of 0.112 g. of the disodium salt in 2.0 ml. of water was sprayed on to 15 g. of tobacco (Philip Morris uncased filler). The cigarettes made from this tobacco, on smoking, gave the characteristic minty flavor of menthofuran.

scribed in Example 1, and the volatile products were examined by gas chromatography and paper chromatographic techniques. In the case of the myrcene adduct, 14.3 mg. of myrcene was formed from 0.10 g. of the disodium salt, along with trace amounts of other terpenoid compounds. From 0.10 g. of the alpha-phellandrene adduct disodium salt, the only volatile products observed were alpha-phellanrene, 3.7 mg., and p-cymene, 14.7 mg. No volatile compounds were observed from the sorbic acid adduct trisodium salt. In each case, no maleic acid or other products arising from the dienophile, maleic anhydride, were found.

Example 4

The adduct from furan and acetylenedicarboxylic acid was prepared by the method of Diels and Alder, Annalen 490, 243 (1931). Neutralization of the adduct to a phenolphthalein end point with normal potassium hydroxide and evaporation of the resulting solution yielded the dipotassium salt, a white, odorless infusible solid.

Pyrolysis of 0.10 g. of the dipotassium salt at 750° C. in air by the procedure described in Example 1, gave 15 mg. of furan, identified by gas chromatography, as the only detectable volatile product. Paper chromatographic experiments demonstrated that no acetylenedicarboxylic acid, propiolic acid, or other volatile acids were present in the pyrolysate.

A solution of .03 g. of the dipotassium salt in 1 ml. of water was sprayed onto 10 g. of tobacco, which was then made into cigarettes.

One of these cigarettes was smoked on a constant pressure smoking machine having a constant puff volume of 35 ml. Seven puffs were taken. The gas phase smoke, after passage through a Cambridge filter, was injected into a 300 foot squalane-coated capillary column having a flame gauge ionization detector. The furan resulting from the added dipotassium salt was identified by comparing the intensity of the furan peak at 11.28 minutes with the intensity of the same peak in the chromatographic pattern of gas phase smoke from an untreated control cigarette smoked in the same manner. The amount of added furan was estimated at 106 micrograms per cigarette.

Example 5

The adduct from acetylenedicarboxylic acid and cyclopentadiene was prepared by the literature procedure (Diels and Alder, Annalen 490, 236 (1931), and was converted to its disodium salt by neutralizing with normal sodium hydroxide to a phenolphthalein end point and evaporating the resulting solution. The disodium salt was an odorless, white solid.

The method given in Example 1 was used to pyrolyze 0.10 g. of the salt at 750° C. The only volatile product was cyclopentadiene, 7.9 mg., identified by gas chromatography. No acetylenedicarboxylic acid or other volatile acids could be detected by paper chromatography, using the system described in Example 1.

Example 3

The literature procedures were followed for the preparation of maleic anhydride adducts from alpha phellandrene (Diels and Alder, Annalen, 460, 98 (1928)), myrcene (Goldblatt and Palkin, J. Am. Chem. Soc. 63, 3517 (1941) ), and sorbic acid (Farmer and Warren, J. Chem. Soc. 1929, 897). The adducts were converted to their disodium salts by allowing them to react with the calculated amount of 1 N sodium hydroxide in aqueous solution for 4 hours (8.6 ml. base/gram of adduct for the phellandrene and myrcene adducts; 14.3 ml. base 1 gram of adduct for the sorbic acid adduct). The salts were isolated by evaporation of their solutions, and were, in each case, white odorless solids which did not melt below 320° C.

These salts were pyrolyzed at 750° C. in air as de-

Example 6 60

Isoprene, 20.4 g., and cinnamaldehyde, 26.4 g., were heated in a sealed tube at 200° C. for 17 hours. Distillation of the crude reaction mixture gave 23.1 g. of the Diels-Alder adduct, l-methyl-5-phenylcyclohexene-405 carboxaldehyde, as a colorless, odorless, oil having a boiling point of 110—111° C. at 1.5 mm. Hg.

One gram of the adduct was absorbed on 0.50 g. of Chromosorb W¹ having a particle size of 80/100 mesh, and the resulting mass was heated at 750° C. for 45 70 seconds in a stainless steel needle under an atmosphere comprising a slow stream of nitrogen. The resulting pyrolysate was collected in a trap cooled with liquid nitrogen. The pyrolysate was analyzed by gas chroma ¹ A form of diatomaceous earth, used to allow collection of 75 the adduct in solid form.

3,047,433

Π tography, using a 4 foot Carbowax ² filled column and a programmed heater operating between 50° and 200° C. The major pyrolysis products were isoprene and cinnamaldehyde. Minor, trace components of the pyrolysis mixture were identified as benzene, toluene, dipentene, and styrene.

A solution of .050 g. of the adduct in 2.0 ml. of ethanol was sprayed onto 10.0 g. of tobacco (uncased Philip Morris filler). The tobacco, after equilibration, was made into cigarettes. These cigarettes, when smoked, had a pleasing cinnamon flavor due to the cinnamaldehyde released into the smoke stream from pyrolysis of the adduct. The isoprene released from pyrolysis of the adduct did not affect the flavor, since the amount released was much less than the amount of isoprene normally present in gas phase cigarette smoke.

Example 7

Cyclopentadiene, 49.5 g., and vinyl acetate, 74.1 g., were sealed in a heavy walled Pyrex tube and heated at 185° C. for 12 hours.

Distillation of the reaction mixture yielded 47.5 g. of the adduct, dehydronorbornyl acetate, having a boiling point of 73°-77° C. at 14 mm., Hg as a colorless oil with a faint ester odor.

This adduct was pyrolyzed under conditions similar to those occurring in a burning cigarette. The experimental procedure for the pyrolysis was the same as that given in Example 6. The pyrolytic products from this adduct were analyzed by vapor phase chromatography and by the mass spectrometer. The products were cyclopentadiene and vinyl acetate. In addition, traces of acetaldehyde, acetone, and benzene were found.

Since certain changes may be made in the above compositions of matter and methods and different embodiments of the invention could be employed without departing from it scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.