Synthetic Studies on Coenzyme Q10. Part 3

An efficient and stereoselective approach to the synthesis of coenzyme Q₁₀ is described (Scheme). The MeOCH₂‐protected p‐hydroquinone 4 containing the C₅ (E)‐allyl (tert‐butyl)dimethylsilyl ether moiety was obtained via a halogen–lithium exchange of the MeOCH₂‐proctected 2‐bromo‐5,6‐dimethoxy‐3‐methylhydroquinone 2 and subsequent addition to (E)‐(^tBuMe₂Si)‐OCH₂C(Me)=CHCH₂Br ( 3 ). The reductive desulfonylation of compound 8 , obtained from 4 via 5 – 7 , was successfully carried out by employing Li/EtNH₂.