Synthesis of Seven-Membered Cross-Conjugated Cyclic Trienes by 8π Electrocyclic Reaction.

A method for the synthesis of 3-methylene-1,4-cycloheptadiene derivatives via an 8π electrocyclization reaction was developed. The triene substrate bearing a phosphate or carbamate group was prepared from γ,δ-unsaturated esters and α,ß-unsaturated aldehydes in four steps. Upon treatment with NaHMDS or KHMDS, the substrate formed a heptatrienyl anion, which underwent electrocyclization and subsequent ß-elimination of the leaving group. The product could be converted into a tropylium salt in two steps.

A new variant of fused cyclic ether synthesis based on Ireland-Claisen rearrangement and RCM.

A new variant of fused cyclic ether synthesis based on Ireland-Claisen rearrangement and ring-closing olefin metathesis (RCM) was developed. The Ireland-Claisen rearrangement of a (Z)-3-alkoxyprop-2-en-1-yl glycolate ester having a cyclic ether on the oxygen at C3 of the (Z)-prop-2-en-1-yl group stereoselectively produced an anti-alpha,beta-dialkoxyester, which was successfully transformed to a fused bicyclic ether via a reaction sequence including RCM.