Tetrahedron

π-Cyclizations of α-methoxycarbonyl oxycarbenium ions; synthesis of oxacyclic carboxylic esters

LDM Lolkema, H Hiemstra, C Semeyn, WN Speckamp

Index: Lolkema, Lucie D. M.; Hiemstra, Henk; Semeyn, Cindy; Speckamp, W. Nico Tetrahedron, 1994 , vol. 50, # 24 p. 7115 - 7128

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Citation Number: 45

Abstract

Acid-mediated cyclization reactions are described of seven methyl 2-acetoxy-2-(3-alken-1- oxy) acetates with different chain substitution. The major product of the tin tetrachloride- induced cyclization reaction is in most cases a tetrahydropyran containing an equatorial carbomethoxy function at C2 and an axial chlorine atom at C4. The mechanism of its formation involves a net cis-addition of the intermediate α-ester oxycarbenium ion to the ...