Thio anion

An example of synthesis of a thiodisaccharide exploiting procedure (a) is reported in Fig. 23. Saponification of glycopyranosyl thioacetate 48 generated the thio-anion 49 which displaced a triflate in position 4 of galacto-derivative 50, generating the thiodisaccharide 51.52... 

Asymmetric syntheses based on the same strategy have been reported - both sugar-derived (Scheme 12.60) [131] and oxazohdine auxiliaries (Scheme 12.61) [132] enable dynamic kinetic resolution. Apphcation of a-thioorganostannanes to this procedure enables access to an enantio-enriched a-thio anion to furnish alcohols in high enantiomeric excess by reactions with a variety of carbonyl compounds [133]. 

Yet another general synthesis which relies on sulphur stabilized carbanions is Seebach s method for converting ketones into a-haloesters with the addition of one carbon atom (Scheme 32). The reaction sequence with aldehydes affords aa-dihaloesters for the conversion of aldehydes to the monohaloesters, the disilyl-thio anion (111) must be used. 

The thio anions (n = 3-6) provide a set of systems to contrast the alter-... 

A thio anion is a material of general formula SX capable of bearing a formal charge on the sulfur. 

An anthio anion is an anion capable of adding sulfur to form a thio anion. 

In Table VI the E and H values have been computed for four thio anions using the kinetic data of Ogston el al. (1948) on the mustard cation. 

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