Carbonate Extension. A Versatile Procedure for Functionalization of Acyclic Homoallylic Alcohols with Moderate Stereocontrol

Article abstract of DOI:10.1021/jo00142a002

Iodocyclization of a series of homoallylic tert-butyl carbonates is an efficient and moderately erythro stereoselective method for the functionalization of homoallylic alcohols with 1,3 relative asymmetric induction.Comparison with the anionic carbonate cyclization process of Cardillo et al.⁴ reveals a similar stereoselectivity for the two methods.Experiments with a number of carbonate derivatives (tert-butyl, benzyl, and 4-methoxy- and 2,4-dimethoxybenzyl) show that loss of the alkyl cation from cyclic intermediate 16 is rate determining.Depending on the cleavage conditions employed, the cyclic iodo carbonates (e.g.,9) can be converted with high selectivity to the iodohydrin methyl carbonate 18, epoxy methyl carbonate 19, or epoxy alcohol 20, offering a significant advantage over our previously reported phosphate cyclization method.