Methyl 3-phenylsulfonyl orthopropionate: A new reagent for cyclopentannulation

S De Lombaert, I Nemery, B Roekens, JC Carretero…

Index: Lombaert, Stephane De; Nemery, Isabelle; Roekens, Bertrand; Carretero, Juan Carlos; Kimmel, Tamar; Ghosez, Leon Tetrahedron Letters, 1986 , vol. 27, # 42 p. 5099 - 5102

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Citation Number: 34

Abstract

A Claisen-type cyclisationt81 of 2 was precluded by the presence of the base-sensitive phenylsulfonyl group. Therefore the specific lithium enolate 3 was trapped with trimethylsilyl chloride to give 4 which was washed with brine to remove HMPA t-3). Treatment of crude 4 with a catalytic amount of trimethylsilyl triflate(101 smoothly effected the cyclisation. Compound 5 was obtained in 68% overall yield as a single diastereoisomer.