The Friedel-Crafts allylation of a prenyl group stabilized by a sulfone moiety: expeditious syntheses of ubiquinones and menaquinones.
An efficient synthetic method for the protected p-hydroquinone compounds 4 containing the C5 trans allylic sulfone moiety has been developed by the direct Friedel-Crafts allylation of the protected dihydroquinone 2 with 4-chloro-2-methyl-1-phenylsulfonyl-2-butene (7a) or 4-hydroxy-2-methyl-1-phenylsulfonyl-2-butene (7b). Expeditious total syntheses of coenzyme Q-10 and vitamin K2(20) have been demonstrated from these valuable key compounds 4a and 4b.