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Short Paper | Regular issue | Vol 94, No. 12, 2017, pp.2299-2306
Published online, 26th October, 2017
DOI: 10.3987/COM-17-13820
Regioselective DMAD-Insertion Reaction of Silyl Dienol Ether of γ-Pyrone under Catalyst- and Heating-Free Conditions

Ichiro Hayakawa,* Yuji Yamanaka, Koichi Mitsudo, Hiromi Ota, and Akira Sakakura*

*Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan

Abstract

The reaction of silyl dienol ether of γ-pyrone with dimethyl acetylenedicarboxylate (DMAD) gives the regioselective insertion product in 66% yield. This DMAD-insertion reaction is thought to include a three-step sequence: (1) thermal [2+2]-type cycloaddition reaction of silyl dienol ether of γ-pyrone with DMAD, (2) ring-opening electrocyclic reaction of the cyclobutene skeleton, and (3) hydrolysis of the silyl dienol ether. The present reaction proceeds under mild conditions without any catalysts or heating. In addition, the [2+2]-type cycloaddition reaction proceeds regioselectively at the C3–C4 double bond in the silyl dienol ether of γ-pyrone.