Polar cycloaddition of 1-benzothiopyrylium salts with conjugated dienes and some transformations of the cycloadducts

H Shimizu, S Miyazaki, T Kataoka

Index: Shimizu, Hiroshi; Miyazaki, Shojiro; Kataoka, Tadashi Journal of the Chemical Society - Perkin Transactions 1, 1996 , # 18 p. 2227 - 2235

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Abstract

Polar cycloaddition of 1-benzothiopyrylium salts 2 with conjugated dienes proceeds regio- and stereo-specifically to afford the corresponding benzo-fused bicyclic sulfonium salts 4 in good yields. Reaction of the cycloadducts 4 with nucleophiles such as methanol or water causes ring opening to give 2-(but-2-enyl)-and 2-(but-3-enyl)-substituted 2H-1- benzothiopyrans 5 and 6, respectively. Treatment of the cycloadduct 4hA with a variety of ...