Patent GB-921930-A (GB)
Title: Process for the preparation of polyene carbonyl compounds
IPC: A23L1/275
Filed: 1961-05-10
Abstract: Polyene carbonyl compounds are prepared by condensing an aldehyde with double bonds in at least the a ,b - and g ,d - positions relative to the aldehyde groups, with an excess of an enol-ether of formula <FORM:0921930/IV(a)/1> where one R is an alkyl group with up to 4 carbon atoms, and the other is hydrogen or an alkyl group (1-4C), and R1 is an alkyl (1-4C) in the presence of an alkanol (1-4C) and an acidic condensing agent.  The condensation product, an ether acetal, is hydrolysed with an acidic agent to the carbonyl compound and alcohol formed may be removed by distillation. Aldehydes such as 6-[21,61,61-trimethyl cyclohexen - (1) - yl]-4-methyl-hexadiene-(2,4)-al-(1), 15-[21,61,61-trimethyl-cyclohexen-(1)-yl]-4,9, 13- trimethylpentadecahexaen- (2,4,8,10, 12,14)-yn-(6)-al-(1), 19-[21,61,61-trimethyl-cyclohexen-(11) -yl]-4,8,13,17, tetramethyl-nonadecaoctaen-(2,4,6,8,12,14,16,18)-yn-(10)-al-(1), and 23 - [21,61,61,61 - trimethyl - cyclohexen-(11)-yl]-4,8,12,17,21-pentamethyl tricosadecaene-2,4,6,8, 10,12,16,18,20,22)-yn-al are condensed with enol-ethers such as ethyl or methyl ethers of propen-(1)-(ol)-(1), propen-(2)-ol-(2) and buten-(2)-ol-(2) in the presence of agents such as mineral or Lewis acids or strongly acidic organic acids, preferably boron trifluoride etherate, to yield an ether-acetal which is hydrolysed in an acid medium, preferably in the presence of an antioxidant and in the absence of oxygen and under conditions to distil off the alcohol. Preferred methods use acetic acid, an alkali-metal salt and water at from 50 DEG C. to the boiling point of the mixture or by boiling a solution of the ether acetal in dilute acetic acid under reflux conditions.  Examples describe the preparation of 8 - [21,61,61 - trimethyl - cyclohexen-(11 -yl]-2,6-dimethyl-octatrien-(2,4,6)-al-(1), 17-[21,61, 61-trimethyl - cyclohexen - (11) - yl]-2,6,11,15-tetramethyl - heptadecaheptaen - (2,4,6,10,12,14,16)-yn-(8)-al-(1), 21-[21,61,61-trimethyl-cyclohexen-(11) -yl]-2,6,10,15,19-pentamethyl - heneicosanoraen-(2,4,6,8,10,14,16,18,20)-yn-12-al-(1), 25-[21, 61,61- trimethylcyclohexen-(11)-yl]- 2,6,10,14 19,23 - hexamethyl - pentacosaundecaen - (2,4, 6,8,10,12,14,18,20,22,24)-yn-(16)-al-(1), and 9-[21,61,61- trimethyl cyclohexen- (11)-yl]- 3,7 dimethyl-nonatrien-(3,5,7)-one-(2).  The acetylenic aldehydes may p be used as colouring agents for food stuffs or as intermediates for the preparation of pigments such as apocarotenals or in the preparation of b -carotene.ALSO:Polyene carbonyl compounds, for example 17 - [21, 61, 61 - trimethyl - cyclo hexen - (11) - yl] - 2,6,11,15 - tetramethyl - heptadecaheptaen-(2,4,6,10,12,14,16) - yn - (8) - al - (1); 21 - [21, 61,61 - trimethyl - cyclo - hexen - (11) - yl]-2,6,10,15,19 - pentamethyl - heneicosanonaen-(2,4,6,8,10,14,16,18,20) - yn - (12) - al - (1); 25-[21,61,61 - trimethyl - cyclohexen - (1) - yl]-2,6,10,14,19,23 - hexamethyl - pentacosaundecaen - (2,4,6,8,10,12,14,18,20,22,24) - yn-(16)-al-(1) (see Group IV (b)), are used as colour-imparting agents, for example a yellow to red colour, in foodstuffs or as poultry feed additives to improve the colouring of skin shanks and egg yolks.