Synthesis of functionalized bicyclo[3.2.1]octan-6-ones for diterpenoids: allylsilane directed Pummerer reaction: insertion reactions of diazoketones

The sulfide 5 underwent Pummerer cyclization to give 6, whereas the allyl silane analog 10 produced the bicyclo[3.2.1]octanones 11 and 11a. Extension of this methodology to 15 resulted in 16 without the necessity for allyl silane activation. The intermediate diazoketone 14 on treatment with BF3·OEt2 gave 17, 18 and 19, whereas the saturated adduct 22 on treatment with Rh2(OAc)4 gave 23.