Sulfoxonium cyclic

Aldol addition and related reactions of enolates and enolate equivalents are the subject of the first part of Chapter 2. These reactions provide powerful methods for controlling the stereochemistry in reactions that form hydroxyl- and methyl-substituted structures, such as those found in many antibiotics. We will see how the choice of the nucleophile, the other reagents (such as Lewis acids), and adjustment of reaction conditions can be used to control stereochemistry. We discuss the role of open, cyclic, and chelated transition structures in determining stereochemistry, and will also see how chiral auxiliaries and chiral catalysts can control the enantiose-lectivity of these reactions. Intramolecular aldol reactions, including the Robinson annulation are discussed. Other reactions included in Chapter 2 include Mannich, carbon acylation, and olefination reactions. The reactivity of other carbon nucleophiles including phosphonium ylides, phosphonate carbanions, sulfone anions, sulfonium ylides, and sulfoxonium ylides are also considered. 

From carbodiphosphoranes R3P=C=PR3 and dialkyl-gold(III) halides, cyclic ylide complexes containing four Au-C <7-bonds are obtained in a multiple transylidation reaction (equation 24). Related thiophosphorus ylides and sulfonium and sulfoxonium ylides are equally effective in the formation of Au-C <7-bonds, and a series of analogous gold thiophosphonium and sulfoxonium-methyhde complexes is available (equations 25-27). ... 

An intramolecular cyclization of -hydroxysulfoxides effected by At-chloro-succinimide, A bromosuccinimide, or sulfuryl chloride gives 1,2-oxathietane 2-oxides, for example, 496, via a sulfoxonium salt. These cyclic sulfoxonium intermediates have been suggested in the conversion of /3-hydroxy-sulfoxides to /3-chlorosulfones, and to a,j3-unsaturated sulfones, in the conversion of /3-ethoxycarbonylsulfoxides to alkenes and of /3-hydroxysulfides to /3-hydroxysulfoxides, and in the conversion of 3-hydroxy- 3-vinylsulfoxides (e.g., 497) to useful terpene building blocks. The yields of the products from 497 vary somewhat depending on the stereochemistry about the two chiral centers. The more highly substituted 1,2-oxathietane 2-oxides are the most stable, because of... 

The intramolecular cyclization of Rh(II) carbenoids onto a sulfoxide S atom allows one to obtain stable sulfoxonium six-membered cyclic ylides. Interestingly, even with allylic-type substituents at the S atom, this reaction stops at the stage of ylide formation, the yields attaining 84% (Scheme 28) (88TL6009). 

Not only compounds with thioalkyl groups, but also those with aliphatic or aromatic sulfine groups react intramolecularly with carbenoid groups, as the examples in Schemes 8-63 and 8-64 demonstrate (Moody et al., 1988). In these reactions, cyclic sulfoxonium ylides are obtained. 

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