Phenylselenenyl ketones, addition

The cinchona alkaloid-derived thioureas (237a,b) and their squaramide counterparts (238a,b) have been employed to catalyse the Michael addition of a-alkyl and of-phenylselenenyl ketones R CH(X)COR (X=alkyl, SePh) and the corresponding... 

The Michael addition of organometallic nucleophiles to enones in the presence of copper(I) salts produces enolates which on treatment with phenylselenenyl bromide give a-seleno ketones. For example, the reaction of the zirconium enolate of 15 with a mixture of phenylselenenyl bromide and diphenyl diselenide affords a mixture of diastereomeric (2R)- and (2V)-phenylse-leno)cyclopentanones 16 in 50% and 31 % isolated yield, respectively12. The analogous reaction with phenylselenenyl chloride gives only the tram-isomer in 27% yield formation of the cw-product is not observed12. 

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