Based on C—Se Bond Cleavage in Selenoketals and Seleno orthoesters

Cyclopropanone selenoketals such as (21 R = Ph or Me), which are prepared by ring-closure processes, behave normally when treated with BuLi in to give the corresponding a-lithio-selenides (22). These species are highly nucleophilic, but they are more basic than other selenium-stabilized carbanions. Enhanced nucleophilicity towards carbonyl compounds, at least for (22 R = Me), is observed by generating the carbanion in ether in this solvent, Bu Li (rather than Bu Li) is required. The a-lithio-selenides (22) have been treated with a variety of simple electrophiles, such as aldehydes, ketones, and primary alkyl 

Organic Compounds of Sulphur, Selenium, and Tellurium, SePh Me 

Dumont, D- Van Ende, and A. Krief, Tetrahedron Lett., 1979,485. M. Sevrin and A. Krief, Tetrahedron Lett., 1980,21,585. 

Full experimental details are available for the sequence PhSeCHjLi + ketone or aldehyde -+ ff-hydroxy-selenide - olefin. The action of BuLi on (30) generates (31), and the vinyl carbanion (32) is available in the same way from (33).  

Carbanions produced by the reaction of seleno-orthoesters with BuLi have been treated with common electrophiles e.g. MejSiCl, propylene oxide, primary alkyl halides, aldehydes, and ketones). The syntheses of (34) and (35) are representative. The anion (36) undergoes 1,2-addition with enones, but, in the presence of HMPA, the thermodynamically more stable 1,4-adduct is obtained,  

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Applications Based on C—Se Bond Cleavage in Selenoketals and Seleno-orthoesters. Primary allylic alcohols are available by homologation of aldehydes (Scheme 4). In this method the selenoxide fragmentation (19) - (20) is best done with t-butyl hydroperoxide in the presence of alumina. 

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