DIASTEREOSELECTIVE RADICAL REACTIONS STARTING FROM CYCLIC IODOHYDRIN DERIVATIVES

The stereoselectivity of radical reactions using cyclic iodohydrins an d 2-alkoxy iodides was investigated on a simple model system obtained from indene (see 1a-d). The low level of stereoselectivity inherent to this type of systems could neither be overcome by using large protect ive group on the O-atom of Ic nor by complexation with Lewis acids. Ho wever, starting from the free alcohol Ic, it was possible to obtain ve ry high selectivities (trans/cis > 100:1) by forming an aluminium alko xide derivative upon treatment with methylaluminium bis[2,6-di(tert-bu tyl)-4-methylphenoxide] (MAD) before running the radical reaction. Des pite the high steric demand of these complexes, the reactions gave sat isfactory yields even for the formation of C-C bonds.