Patent GB-945298-A (GB)
Title: 10, 12-hexadecadiene derivatives
IPC: C07C51/42
Filed: 1960-02-25
Abstract: The invention comprises 10,12-hexadecadienoic acid compounds of the general formula CH3.CH2.CH2.CH=CH.CH=CH. (CH2)8 wherein R is the group COOH or COOR11 in which R11 is an alkyl group containing up to 4 carbon atoms. The compounds may be prepared by a first method comprising reacting a 1-halo-2-hexene with triphenyl phosphine, reacting the resulting triphenyl phosphonium halide with a proton acceptor selected from methyl and butyl lithiums, sodium and lithium acetylides, and alkali metal and alkaline earth metal alkoxides and amides to give a phosphorane having the formula (C6H5)3 P=CH.CH=CH.CH2.CH2.CH3 which is condensed with a 10-decanal-1-acid ester OCH. (CH2)8COOR11 giving the desired hexadecadienoic acid ester which may be saponified and then acidified to give the free acid. The ester product on reduction with a complex metal hydride yields a mixture of isomers of 10,12-hexadecordien-1-ol which may be separated by fractional crystallisation.  The esters on saponification and acidification yield a mixture of 10-trans, 12-trans and 10-cis, 12-trans hexadecadienoic acids which may be separated by fractional crystallisation and these isomers can be reduced, directly or after conversion into the esters, into the corresponding isomeric 10,12 hexadecadien-1-ols by means of a complex metal hydride.  The esters or free acid may also be prepared by a second method comprising reacting a 1-halo-2 hexene with lithium or magnesium and reacting the resulting organometallic compound with an above mentioned 10-decanal-1-acid ester under the conditions of a Grignard synthesis to form a secondary carbinol CH3.CH2.CH2.CH=CH. CH2. CH(OH). (CH2)8. COOR11 or, alternatively, forming this carbinol by reacting the halo-hexene with the decanal-acid ester in the presence of zinc under the conditions of a Reformatsky synthesis, and then splitting off water from the carbinol, for example by means of P2O5 alone or with pyridine in an inert solvent, the resulting hexadecadienoic acid ester then being saponified and acidified if the free acid is required.  These organo metallic reactions also result in the formation of by-products having the formulae CH3.CH2.CH2.CH (CH=CH2). CH.(OH (CH2)8 COOR11 and, on dehydration, CH3. CH2. CH2. C (CH=CH2)=CH. (CH2)8 COOR11.  In examples, (1) 1-bromo-2-hexene, prepared by reacting PBX3 with 2-hexen-1- ol obtained by reducing 2-hexen-1-ol with lithium aluminium hydride, is reacted with triphenyl phosphine, the resulting phosphonium bromide is reacted with butyl lithium and the resulting phosphorane is condensed with 10-decanal-1-acid methyl ester yielding a cande 10,12-hexadecadienoic acid methyl ester; the ester is saponified and the acid product separated into the above-mentioned two isomers by fractional crystallisation from petroleum ether and the two acids are converted into their methyl esters by reaction with diazo methane; (2) 10-decanal-1-acid methyl ester is reacted with 1- bromo -2-hexene in the presence of zinc dust in tetrahydrofuran yielding a mixture of 10-hydroxy-12-hexadecanoic acid methyl ester and 10-hydroxy-11-vinyl - tetradecanoic acid methyl ester, which is dehydrated by means of P2O5 to give a mixture of the desired 10-12-hexadeca dienoic acid methyl ester and 11-vinyl-10-tetradacenoic acid methyl ester. Specifications 813,539, 893,947