Stereocontrol in Radical Processes through the Exocyclic Effect: Dual Role of Triethylboron as Radical Initiator and in Situ Derivatization Agent

[structure in text] The diastereoselectivity of radical processes involving 1,3-diols is increased significantly with a simple and efficient strategy using the exocyclic effect. Boronate derivatives are successfully formed in situ by treatment of an equimolar amount of Et(3)B in the presence of oxygen. This step is followed by the mediation of a carbon-centered radical alpha to the cyclic boronate to give the anti reduced product with high stereocontrol. The sequence is also extended to beta-amino alcohols.