Synthesis of Functionalized α‐Vinyl Aldehydes from Enaminones

Abstract

An efficient RhII‐catalyzed synthesis of functionalized α‐vinyl aldehydes with high E/Z stereoselectivity was developed. The reaction mediates the cyclopropanation of enaminones with vinyl carbenoids that are generated from cyclopropenes in situ to give the aminocyclopropane intermediates. Selective C−C bond cleavage of the cyclopropane intermediates leads to formation of α‐vinyl aldehyde derivatives with high E/Z selectivity. This method proceeds at room temperature under very mild reaction conditions and works with a broad substrate scope.

Expedient Synthesis of gem-CF2-2H-Thiophenes from Enaminothiones

“…Thus, it would be appealing for wide audiences from interdisciplinary science to design a powerful yet reliable strategy to construct 2 H -thiophenes containing fluorine atoms in the core rings. In our continuing interests in enaminone and carbene chemistry, 20 21 22 23 24 25 26 we envisioned that the possibilities of preparing fluorinated S -heterocycles by cyclization of enaminothiones with fluorinated carbenes, which are both easily available starting materials. Herein, we present an efficient avenue for the synthesis of fluorinated 2 H -thiophenes via a formal [4+1] cyclization of enaminothiones and fluorinated carbene precursors under very mild reaction conditions without any metal catalysts (Figure 1 ).…”

“…On the other hand, since we previous successfully isolated aminocyclopropane intermediate through reaction of carbene precursors with enaminones. 20 It is hard to rule out the possibility that it undergoes cyclopropanation process to afford cyclopropylamine intermediate C as described in path II. Finally, the cyclopropylamine C selectively cleaves the C–C bond and subsequently cyclizes to afford the desired 2 H -thiophene product 3 .…”