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Stereoselective Cyclopropanation of 2‐[( S )‐(4‐Methylphenyl)sulfinyl]cyclopent‐2‐en‐1‐one with Sulfur Ylides and α ‐Halo Carbanions. Preliminary Communication
Author(s) -
Mikołajczyk Marian,
Midura Wanda H.,
Michedkina Elena,
Filipczak Agnieszka D.,
Wieczorek Michał W.
Publication year - 2005
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200590138
Subject(s) - cyclopropanation , chemistry , sulfonium , carbanion , selectivity , sulfoxide , medicinal chemistry , stereoselectivity , stereochemistry , organic chemistry , catalysis , salt (chemistry)
The cyclopropanation of the title compound ( S )‐ 2 with various sulfur ylides has been examined. The reaction with methylenesulfonium ylides gave the corresponding cyclopropanes 4 with low diastereoselectivity. The formation of the second product 5 arising from the subsequent methylenation of the CO group was also observed. A clean cyclopropanation of ( S )‐ 2 took place with ethyl (dimethylsulfanylidene)acetate affording the cyclopropanes 6 , with high π ‐facial selectivity, but low endo / exo ratio. A high endo / exo selectivity, but low π ‐facial selectivity was observed in the reaction of ( S )‐ 2 with (2‐ethoxy‐2‐oxoethyl)(diphenyl)sulfonium tetrafluoroborate. The use of α ‐bromoacetate carbanion as the cyclopropanation reagent resulted in the formation of 6 with very high facial and endo / exo ‐selectivity. In a proposed explanation of the stereochemical outcome of the cyclopropanations investigated, the ground‐state conformation of the sulfoxide 2 and the transition‐state structure of the initial addition step were taken into account.