Mukaiyama Reactions of a Silyl Enol Ether with Heteroatom‐Substituted β‐Formyl Esters

Heteroatom‐substituted aldehydes 3, 4, and 5 were subjected to Mukaiyama reactions with silyl enol ether 10. The reaction of the new trifluoromethyl‐substituted aldehyde 3 with 10 afforded γ‐lactone 11 with excellent trans selectivity. In contrast, the known benzyloxy‐substituted aldehyde 4 and 10 provided γ‐lactone 13 without any selectively in the presence of BF3 as the promoting Lewis acid; use of TiCl4 induced exclusive cis selectivity. Carbamoyl‐substituted aldehyde 5 and silyl enol ether 10 were combined under different conditions, although good diastereoselectivity could not be achieved. The results obtained are discussed in terms of the electronic effects of the substituents and their ability to form chelates.