Patent GB-783389-A (GB)
Title: Process for the manufacture of 15,15-dehydro-beta carotene
Filed: 1955-12-07
Abstract: The invention comprises 1,18 - di[21,61,61-trimethyl - cyclohexen - (11) - yl - (1)] - 2,17 - di-halo - 3,7,12,16 - tetramethyl - octadecahexaen-(3,5,7,11,13,15) - ine - (9), 1,18 - di[11 - halo - 21,61,61 - trimethyl - cyclohexyl - (11) - 3,7,12,16-tetramethyl - octadecaoctaene - (1,3,5,7,11,13, 15,17)-ine-(9) and a process for the manufacture of 15,151-dehydro-b -carotene by treating 1,18-di[21,61,61 - trimethyl - cyclohexen - (11 - yl - (11)] - 3,7,12,16 - tetramethyl - octadecahexaene-(2,4,6,12,14,16) - ine - (9) - diol - (8,11) or 1,18-di[21,61,61 - trimethyl - cyclohexylidene - (11)]-3,7,12,16 - tetramethyl - octadecahexaene - (2,4,6,12,14,16) - ine - (9) - diol - (8,11) or a lower alkanoic acid diester of either compound with hydrohalic acid, e.g. aqueous or anhydrous alcoholic solutions of hydrogen chloride or hydrogen bromide so as to split off two mols. of water or acid therefrom and cause an allyl rearrangement.  The treatment with hydrogen halide may be conducted below about 30 DEG  C. Examples describe the production of 15,151-dehydro b -carotene starting from the free dihydroxy compound or an ester thereof.  The starting compound, 1,18-di[21,61,61-trimethyl - cyclohexylidene - (11)] - 3,7,12,16 - tetramethyl - octadecahexaene - (2,4,6,12,14,16) - ine - (9)-diol-(8,11) is obtained by condensing b -chloro-vinyl ether with 2,6,6-trimethylcyclohexanone-(1) and reducing the product to produce 2,6,6 - trimethyl - cyclohexylidene - (1) - acetaldehyde, which compound is treated with ethanol to produce 2,6,6-cyclohexylidene-(1)-acetaldehyde diethyl-acetal, which compound is treated with ethyl propenyl ether to produce 4 - (21,61,61 - trimethyl - cyclohexylidene - (11)] - 2 - methyl - 1,1,3 - triethoxy - butane, which compound is treated with acetic acid and sodium acetate to produce 4-[21,61,61-trimethyl-cyclohexylidene - (11)] - 2 - methyl - buten - (2) - al - (1), which compound is treated with ethanol to produce 4 - [21,61,61 - trimethyl - cyclohexylidene-(11)] - 2 - methyl - 1,1 - diethoxy - butene - 2, which compound is treated with ethyl vinyl ether to produce 6 - [21,61,61 - trimethyl - cyclohexylidene-(11)] - 4 - methyl - 1,1,3 - triethoxy - hexene - 4, which compound is treated with acetic acid and sodium acetate to produce 6-[21,61,61-trimethylcyclohexylidene - (11)] - 4 - methyl - hexadiene - (2,4)-al-(1), which compound is treated with ethanol to produce 6-[21,61,61-trimethyl-cyclohexylidene - (11)] - 4 - methyl - 1,1 - diethoxy - hexadiene-(2,4), which compound is treated with ethyl propyl ether to produce 8-[21,61,61-trimethyl - cyclohexylidene - (11)] - 2,6 - dimethyl - 1,13 - triethoxy - octadiene - (4,6), which compound is treated with acetic acid and sodium acetate to produce 8-[21,61,61-trimethyl-cyclohexylidene - (11)] - 2,6 - dimethyl - octatriene - (2,4,6)-al-(1), which compound is treated with acetylene in a Grignard reaction to obtain the desired compound. 1,18-Di[21,61,61-trimethylcyclohex - (11) - yl - (11)] - 3,7,12,16 - tetramethyl octadecahexaen - (2,4,6,12,14,16) - ine - (9) - diol - (8,11) may be prepared by condensing acetylene with 8 - [21,61,61 - trimethyl - cyclohexene - (11)-yl - (11)] - 2,6 - dimethyl - octatriene - (2,4,6) - al-1.