Stereochemical outcome of reactions involving 1,1-bis(seleno) 4-tert-butyl cyclohexanes

Stereoselective allylation of conformationally rigid 4-tert-butyl-1,1-bis(methylseleno) cyclohexanes has been achieved (i) from the axial face on sequential reaction with alkyllithiums, copper iodide-dimethyl sulfide and allyl bromides and (ii) from the equatorial face of reaction with allyl stannanes or -silanes in the presence of a Lewis acid. The synthesis of 1-selenocyclohexane has been achieved via the 'carbanionic route' or with tin hydride through a 'radical route'. The former reaction leads selectively to the trans selenides whereas both stereoisomers are produced in the latter process.