Montanari asymmetric

In 1960, Montanari and Balenovic and their coworkers described independently the first asymmetric oxidation of sulfides with optically active peracids. However, the sulphoxides were formed in this asymmetric reaction (equation 130) with low optical purities, generally not higher than 10%. The extensive studies of Montanari and his group on peracid oxidation indicated that the chirality of the predominantly formed sulphoxide enantiomer depends on the absolute configuration of the peracid used. According to Montanari the stereoselectivity of the sulphide oxidation is determined by the balance between one transition state (a) and a more hindered transition state (b) in which the groups and at sulphur face the moderately and least hindered regions of the peracid,... 

This chapter, however, does not deal with above-mentioned reactions of sulfoxides. Rather it is limited to asymmetric synthesis using a-sulfinyl carbanions and -unsaturated sulfoxides, specifically in which the stereogenic sulfoxide sulfur atom is enantiomerically pure. Therefore reactions of racemic sulfoxides are for the most part excluded from this review. For more general discussions, the reader is referred to other chapters in this volume and to other reviews on the chemistry of sulfoxides. Especially useful are the reviews by Johnson and Sharp and by Mislow in the late 1960s and by Oae and by Nudelman as well as a book by Block . A review by Cinquini, Cozzi and Montanari" through mid-1983 summarizes the chemistry and stereochemistry of optically active sulfoxides. This chapter emphasizes results reported from 1984 through mid-1986. 

Yugoslavia. An excellent monograph by Morrison and Mosher (38) provides a comprehensive review of the pre-1969 literature on this subject. The formation of sulfoxides in the asymmetric reaction shown above typically occurred with quite low optical purities (not higher than 10%). The detailed and extensive studies of Montanari and... 

These and other examples of intramolecular asymmetric induction by the sulfinyl group have been discussed by Montanari in his review paper (9). 

With regards to the mechanism of the generation of onium anion, the Starks extraction mechanism and interfacial mechanism (Brandstrom-Montanari modification) are suggested (Scheme 1.7). As in the above-described case, the interfacial mechanism seems to be operative in the asymmetric phase-transfer catalysis. 

Pozzi G, Banfi S, Manfredi A, Montanari F, Quid S (1996) Tetrahedron 52 11879 Pozzi G, Montanari F, Quid S (1997) J Chem Soc Chem Common 69 a) Jacobsen EN, (1993) Asymmetric Catalytic Epoxidation of Unfunctionalized Olefins. In Ojima I (ed) Catalytic Asymmetric Synthesis. VCH, Weinheim, b) Katsuki T (1996) J Mol Cat 113 87... 

Montanari has also applied chiral sulfinamide methodology to the asymmetric synthesis of methyl aryl sulfoxides [25]. (5)-(-)-p-Toluene sulfinamides (14) were prepared from (5)-(-)-menthyl p-toluene sulfinate and the corresponding bromomagnesium dialkylamides in moderate yield and good enantioselectivity (Scheme 2.15). 

Montanari and co-workers have prepared the first example of an optically active aziridine where the asymmetry is solely due to a tervalent, nonbridgehead nitrogen atom. Asymmetric chlorination of 2,2-diphenylaziridine with either (lR,2/ )-(—)-isobomyl hypochlorite or the (-f)-W-chloro-sulphoximine (651) gave reasonable yields of optically active 7V-chloro-2,2-diphenylaziridine. 

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