The synthesis of d 6 ‐α‐farnesene

D 6 ‐α‐Farnesene (3,7‐dimethyl‐11‐ 2 H 3 ‐methyl‐12,12,12‐ 2 H 3 ‐dodeca‐1,3E,6E,10‐tetraene) has been synthesised by two routes. Thermolysis of 2‐geranyl‐3‐methylsulpholene (5) yielded unlabelled α‐farnesene (93%) which was epoxidized at Δ10 in 31% yield. Oxidative cleavage of the epoxide (42%) and Wittig elaboration of the resultant trienal with d 6 ‐isopropyl triphenylphosphorane gave d 6 ‐α‐farnesene (73%). Alternatively, selective epoxidation of ( 5 ) gave the terminal 6′,7′ mono‐epoxide in 74% yield. Oxidative cleavage (73%) and Wittig elaboration of the resultant aldehyde yielded deuterated 2‐geranyl‐3‐methylsulpholene (46%). Thermal elimination of sulphur dioxide afforded the title compound in 91% yield.