1.3- Dithianes organolithium compounds

The most varied types of organolithium compounds are nowadays used in syntheses. For example, 2-lithio-l,3-dithianes, as protected acyllithium derivatives (Eq. 288), are suitable reagents for hydroxyalkylation with oxiranes (Eq. 

Carbolithium compounds of moderate reactivity open the O—C bond of cyclic sulfate esters or cyclic sulfamidates to produce new C—C links, as shown, for example, in equation 112 for a chiral cyclic sulfamidinate and 2-lithio-l,3-dithiane (380a). More reactive organolithium species, such as n-BuLi and PhLi, yield mixtures of products, probably due to attack on the S atom of the sulfonamido group too °. 

Carbon nucleophiles which do not readily trigger the rearrangement of epoxides include lithiated dithianes [295, 304], lithiated sulfones [238], lithiated diarylphos-phine oxides [240, 305], lithium enolates [306], and allylic organolithium or organo-magnesium compounds [298, 307-310] (Scheme4.67). 

Dithianes are ring opened by organolithium reagents and subsequent reaction with electrophiles provides unsymmetrically substituted dithia compounds (95JCS(P1)2381). 

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