Synlett 2006(20): 3540-3544  
DOI: 10.1055/s-2006-958409
© Georg Thieme Verlag Stuttgart · New York

Oxidative Kinetic Resolution of Alkyl Aryl Sulfoxides

Iraj Mohammadpoor-Baltork, Mathias Hill, Lorenzo Caggiano*, Richard F. W. Jackson*
Department of Chemistry, Dainton Building, University of Sheffield, Brook Hill, Sheffield, S3 7HF, UK
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Further Information

Publication History

Received 30 August 2006
Publication Date:
08 December 2006 (online)


Kinetic resolution is observed in the oxidation of racemic alkyl aryl sulfoxides using a combination of VO(acac)2 and ligand 1 in chloroform at 0 °C, conditions previously described for asymmetric oxidation of prochiral sulfides. Kinetic resolution is also ­observed in toluene as the solvent, although higher temperatures are required.


The ratios of response factors for each sulfoxide and sulfone at 252 nm were determined as follows: R = Me; Ar = Ph (9.9), p-BrC6H4 (7.5), p-ClC6H4 (16.5), p-Tol (12.7), p-MeOC6H4 (1.8), p-NO2C6H4 (0.56), 2-Naphth (4.9): R = Et, Ar = Ph (10.0).


HPLC-grade chloroform was purchased from Fisher Scientific, stabilized with amylene (100 ppm). Since CHCl3 can also be stabilized with a small amount of alcohols, and may contain HCl, we investigated the effects of these additives in the kinetic resolution reaction. Using dried CHCl3 gave very similar results to those observed using either unpurified CHCl3 or dried CHCl3 with 1 mol% of 2 M HCl. Interestingly, however, the addition of 0.5 mol% of i-PrOH gave moderate conversion (35%) to the sulfone and racemic sulfoxide.


In our experience, use of 23 mL of solvent per mmol of substrate as originally reported results in slow reactions and much poorer yields, a problem that can be overcome by drastically reducing the amount of solvent. Alonso and Nájera have made similar observations when conducting larger-scale reactions: Alonso D. A. and Nájera, C., personal communication from Alonso, D. A., August 2006.