Patent GB-790613-A (GB)
Title: Novel unsaturated aldehydes and a process for the manufacture thereof
Filed: 1955-08-16
Abstract: The invention comprises unsaturated aldehydes having the general formula: <FORM:0790613/IV (b)/1> wherein R stands for (2,6,6-trimethylcyclohexylidene) - methyl or [2,6,6 - trimethylcyclohexen - (2) - ylidene] - methyl or [2,6,6-trimethyl - cyclohexadien - (1,3) - yl] - methyl and a process for the preparation thereof which includes acetalizing iso- or retrodehydro- or b -dehydro-C16-aldehyde in a manner known per se, condensing the resulting iso- or retrodehydro-or b -dehydro-C16-acetal with an alkyl propenyl ether in the presence of an acidic condensing agent and heating the iso-, retrodehydro- or b -dehydro-C19-ether acetal so obtained in an aqueous acid medium.  The iso-, retrodehydro and b -dehydro C16 aldehydes employed as starting materials are represented by the formula: <FORM:0790613/IV (b)/2> wherein R has the above significance.  The iso-, retrodehydro- and b -dehydro-C16-acetals are the corresponding acetals.  The iso-, retrodehydro-and b -dehydro-C19-ether acetals are 8-[21,61,61-trimethyl - cyclohexylidene] -; 8-[21,61,61-trimethyl - cyclohexen - (21) - ylidene]- and 8 - [21,61,61 - trimethyl - cyclohexadien - (11,31)-yl] - 2,6 - dimethyl - octadiene - (4,6) - ether - (3)-acetal-(1) respectively.  The acetalization may be carried out using an aliphatic orthocarboxylic acid triester, e.g. triesters of lower aliphatic orthocarboxylic acids with lower aliphatic alcohols, e.g. methyl, ethyl or butyl esters of orthoformic acid, in the presence of an acid condensation agent, e.g. boron trifluoride etherate, zinc chloride, ammonium nitrate, phosphonic acid or p-toluene sulphonic acid.  Condensation agents for use in the record step include boron trifluoride etherate, zinc chloride, titanium chloride, aluminium trichloride, ferric chloride and tin tetrachloride. Preferred propenyl ethers are those derived from the same alcohol as the acetalizing groups, e.g. methyl-, ethyl- or butyl butenyl ethers. The third step of the process is carried out in the presence of water-soluble organic or inorganic acids such as p-toluene sulphonic, acetic, propionic, oxalic, sulphuric or phosphoric acid or water-soluble salts having an acid reaction, e.g. zinc chloride on sodium bisulphate.  Oxygen may be excluded and hydroquinone added.  A water-miscible solvent, e.g. dioxane, tetrahydrofuran or ethylene-glycol dimethyl ether may be added. In examples: b -dehydro-C19-aldehyde is obtained by treating b -dehydro-C16-aldehyde with ethyl orthoformate in the presence of orthophosphoric acid and ethyl alcohol to obtain the diethyl acetal of the aldehyde which treated with propenyl ether in the presence of zinc chloride to obtain b -dehydro-C19-(ethyl ether)-diethyl acetal which is heated with glacial acetic acid, sodium acetate, water and hydroquinone (1) retrodehydro-C19-aldehyde is similarly obtained from retrodehydro-C16-aldehyde (2); and isoC19-aldehyde is similarly obtained from iso-C16-aldehyde.  Iso-C16-aldehyde is obtained by condensing ethoxy acetylene with 2,6,6-trimethyl-cyclohexanone-(1) to obtain an ethoxy-(acetylenic carbinol) which is partially hydrogenated and treated with acid to obtain (2,6,6-trimethylcyclohexylidene)-acetaldehyde which is acetolized, the acetal is condensed with a propenyl ether, the condensation product is treated with acid, the 4-(21,61,61-trimethyl-cyclohexylidene) 2-methyl-buten(2)-al-(1) produced is acetalized, the acetal is condensed with a vinyl alkyl ether and the product is treated with an acid.  Alternatively 2,6,6-trimethyl-cyclohexanone-(1) is obtained by condensing it with 2-methyl-1-methoxy-2-hydroxy-butine-(3) in a Grignard reaction, partially hydrogenating the resulting acetylene-glycol at the triple bond, dehydrating the hydrogenation product, treating the dehydration product with acid, acetalizing the 4 - (21,61,61 - trimethyl - cyclohexylidene) - 2 - methyl-buten-(2)-al-(1), condensing the acetal formed with a vinyl alkyl ether and treating the condensation product with an acid.  Retrodehydro-C16-aldehyde is obtained by condensing ethoxyacetylene with 2,6,6 - tri - methyl - cyclohexen - (2) - one - (1) to obtain an ethoxy-(acetylenic carbinol), partially hydrogenating the latter and treating the product with acid, acetalizing the (2,6,6-trimethylcyclohexen - (2) - ylidene) - acetaldehyde obtained, condensing the acetal with a propenyl alkyl ether, treating the product with acid to obtain 4 - [21,61,61 - trimethyl - cyclohexen - (21) - ylidene] - 2 - methyl - buten - (2) - al - (1), acetalizing the latter and condensing the acetal with a vinyl alkyl ether and treating the product with an acid. Alternatively b -ionone is condensed with ethyl chloro-acetate, the glycide ester is saponified with alkali, the 4-(21,61,61 trimethyl - cyclohexen - (11) - yl] - 2 - methyl - buten - 2 - al - (1) obtained is brominated with N-bromo-succinimide, the product obtained is treated with quinoline, the 4-[21,61,61-trimethy cyclohexen - (21) - ylidene] - 2 - methyl - buten - (2)-al-(1) obtained is acetalized, the acetal is condensed with vinyl alkyl ether and the product obtained is treated with acid.  b -Dehydro-C16-aldehyde is obtained by condensing b -ionone with ethyl chloroacetate in a glycide ester reaction, subjecting the product to alkaline saponification, dehydrogenating the 4 - (21,61,61 - trimethyl - cyclohexen - (11) - yl] - 2 - methyl - buten - (2) - al - (1) obtained by treatment with N-bromo-succinimide and quinoline, converting the 4-[21,61,61-trimethyl-cyclohexen - (21) - ylidene] - 2 - methyl - buten - (2) - al-(1) with isopropenyl acetate into the enol acetate, hydrolysing the latter, acetalizing the 4 - [2,6,6 - trimethyl - cyclo - hexadien - (11,31) - yl] - 2 - methyl - buten - (2) - al - (1) formed, condensing the acetal with vinyl alkyl ether and treating the condensation produced with an acid.  Specifications 786,003, 790,611, 790,612 and 790,614 are referred to.ALSO:Foods containing animal and vegetable fats may contain as antioxidant an aldehyde of the general formula: <FORM:0790613/VI/1> wherein R stands for (2,6,6-trimethyl-cyclohexylidene) - methyl or [2,6,6 - trimethylcyclohexen - 2 - ylidene] - methyl or [2,6,6 - trimethyl - cyclohexadien - (1,3) - yl] - methyl (see Group IV (b)). Specifications 786,003, 790,611, 790,612 and 790,614, [all in Group IV (b)], are referred to.