Studies on the organic reactions using $Sc(OTf)_3$supported on CMK-5

Abstract

Addition reactions to carbonyl and related compounds are among the most fundamental and important reactions in organic chemistry. It is well-recognized that aldimines are less reactive than aldehydes toward nucleophilic addition1 because of the difference in electronegativity between oxygen and nitrogen, in addition to the steric hindrance of aldimines, etc. It was first observed that reactions of imines with silyl ketene acetals proceeded smoothly in the presence of $Sc(OTf)_3$ to afford the corresponding β-amino ester derivative in a moderate yield. The yield was improved when $Sc(OTf)_3$ was used instead of $Yb(OTf)_3$ as a catalyst. Thus we investigated the organic reaction using scandium triflate. The possibility of $CMK-5/Sc(OTf)_3$ as a Lewis acid was suggested to us. Studies aimed at the total synthesis of cameroonanol using alkylidene carbene generated from alkynyliodonium salts to syntheses of angulary fused tricyclopentanoid (triquinane structure) have been performed. As preliminary studies, generation and reactivity of alkylidene carbenes from alkynyliodonium salt was studied. In this study, we investigated the synthesis of angular triquinanes using alkylidene carbene generated from alkynyl(phenyl)iodonium salt. In the synthesis of triquinanes, the key step of the reaction sequence utilized an intramolecular 1,3 diyl trapping via a cyclopropanation of alkylidene carbene. The cyclization reaction seemed that the moiety of precursor having alkynyliodonium salt played a significant role in the synthesis of triquinane and reactivity of alkylidene carbene. As the [2+3] cycloaddition reaction of trimethylenemethanes (TMMs) diyl has been applied to the total synthesis of Cameroonanol.