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■ A Molecular Orbital Calculation Study on Ring-Opening Reactions of Fluorine-Containing 3,4-Dihydro-2H-pyrans with Amines and Thiols

Norio Ota, Yasuhiro Kamitori,* Yusuke Tamai, Guo Feng, Mizuki Hatakenaka, and Etsuji Okada*

*Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan

Abstract

The reactions of 5-trifluoroacetyl-6-trifluoromethyl-3,4-dihydro-2H-pyran (1a) with various amines and sodium thiolates gave the corresponding 4,4-bistrifluoroacetyl-1,3-butadienyl amines (2b) and sulfides (2c), respectively, in good yields. Our DFT calculations suggested that the elimination of isobutanol from 1a and the subsequent electrocyclic ring-opening reaction on intermediate (4a) would proceed to afford 4,4-bistrifluoroacetyl-1,3-butadienyl ether (2a). Moreover, subsequent nucleophilic O-N and O-S exchange reactions on 2a which gave 2b and 2c, respectively, were also predicted.