Open AccessStereochemical aspects of the Pummerer reaction. Diastereotopic selectivity in the deprotonation of oxysulfonium cations
Author(s) -
Saul Wolfe,
Peter M. Kazmaier
Publication year - 1979
Publication title -
canadian journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.323
H-Index - 68
eISSN - 1480-3291
pISSN - 0008-4042
DOI - 10.1139/v79-385
Subject(s) - chemistry , pummerer rearrangement , sulfoxide , deprotonation , acetic anhydride , trifluoroacetic anhydride , tetrahydrofuran , kinetic isotope effect , deuterium , medicinal chemistry , selectivity , dication , organic chemistry , solvent , catalysis , ion , physics , quantum mechanics , molecule
The diastereomeric RS/SR- and RR/SS-benzyl-α-d methyl sulfoxides have been subjected to the Pummerer reaction with acetic anhydride and with trifluoroacetic anhydride. The ethoxysulfonium fluoroborate derivatives of these sulfoxides have been subjected to the Pfitzner–Moffatt reaction with sodium hydride in tetrahydrofuran. The deuterium contents of the starting materials and of the Pfitzner–Moffatt product have been determined by mass spectrometry. The deuterium contents of the α-acyloxybenzyl methyl sulfoxides formed in the Pummerer reaction have been determined by 1 Hmr spectroscopy. The resulting data permit the calculation of the diastereotopic selectivities and isotope effects associated with the deprotonation of oxysulfonium cations. The selectivities are found to be lower by a factor of about 10 than those observed in the formation of the benzyl-α-d methyl sulfoxides by hydrogen–deuterium exchange of benzyl methyl sulfoxide. Nevertheless, the existence of selectivity in the Pummerer reactions rules out a sulfurane and a dication as sole product-determining intermediates. The factors contributing to this low selectivity are discussed.