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Enantioselective oxidation of sulfides catalyzed by titanium complexes of 1,2‐diarylethane‐1,2‐diols: Effect of the aryl substitution
Author(s) -
Superchi Stefano,
Scafato Patrizia,
Restaino Lina,
Rosini Carlo
Publication year - 2008
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.20456
Subject(s) - chemistry , enantioselective synthesis , aryl , catalysis , titanium , substitution (logic) , organic chemistry , medicinal chemistry , combinatorial chemistry , alkyl , computer science , programming language
The effects of the substitution on the aryl moiety on the asymmetric oxidation of sulfides mediated by Ti‐complexes of chiral 1,2‐diarylethane‐1,2‐diols were investigated. The substitution of the aryl ring of the diol with both EWG and EDG substituents generally decreased the enantioselectivity with respect to the use of unsubstituted 1,2‐diphenylethane‐1,2‐diol ( 1a ). Only in the presence of 1,2‐di(4‐ t ‐butyl)phenyl‐1,2‐diol ( 1g ) were higher ee's obtained with aryl methyl and aryl benzyl sulfides affording ee's up to 90 and 99%, respectively. Lower ee's were achieved with larger naphthyl and aryl alkyl sulfides. Contrary to the other Ti‐alcoholates used in the oxidation of sulfides, the Ti‐complex of diol 1g was soluble in hexane, allowing us to perform the process with high enantioselectivity in this solvent, with great environmental advantages over the commonly used chlorinated solvents. Chirality, 2008. © 2008 Wiley‐Liss, Inc.