Coupling reaction involving a Grignard and allylic halide

A process for the synthesis of 3,7,11,15-tetramethylhexadec-6-ene, 7-methylene-3,11,15-trimethylhexadecane, or a compound having the same arrangement of carbon atoms and additional points of unsaturation, from a C.sub.10 acyclic terpene hydrocarbon compound of the 2,6-dimethyloctane series, having a terminal isopropenyl or isopropylidene group, and a linear C.sub.10 aliphatic hydrocarbon having an alkyl or alkenyl radical R comprising the steps of;

• (a) halogenating said C.sub.10 acyclic hydrocarbon to produce an allylic halide having a halogen allylic to a terminal olefinic site;
• (b) forming the Grignard reagent RMgX of said C.sub.10 aliphatic hydrocarbon, X being halogen;
• (c) preparing a reaction mixture comprising said Grignard reagent and said allylic halide;
• and
• (d) removing from said reaction mixture a C.sub.20 compound in which coupling of the Grignard reagent and allylic halide occurs by displacement by R of the Grignard reagent at the terminal olefinic site of the allylic halide accompanied by double bond migration and loss of halide.

A process for the synthesis of a C.sub.15 compound selected from the group consisting of 10,11-dihydrofarnesene, farnesene, isomers of 10,11-dihydrofarnesene and farnesene, or a compound having the same arrangement of carbon atoms and fewer sites of unsaturation from a C.sub.10 acyclic terpene hydrocarbon compound of the 2,6-dimethyloctane series, having a terminal isopropenyl or isopropylidene group, and a linear C.sub.5 aliphatic hydrocarbon having an alkyl or alkenyl radical R comprising the steps of;

• (a) halogenating said C.sub.10 acyclic hydrocarbon to produce an allylic halide having a halogen allylic to a terminal olefinic site;
• (b) forming the Grignard reagent RMgX of said C.sub.5 aliphatic hydrocarbon, X being halogen;
• (c) preparing a reaction mixture comprising said Grignard reagent and said allylic halide;
• and
• (d) removing from said reaction mixture said C.sub.15 compound in which coupling of the Grignard reagent and allylic halide occurs by displacement by R of the Grignard reagent at the terminal olefinic site of the allylic halide accompanied by double bond migration and loss of halide.