Pd-Catalyzed Asymmetric Allylic Cycloaddition of Vinyloxetanes with Formaldehyde.

An efficient method for the enantioselective construction of tertiary 1,3-diols via Pd-catalyzed asymmetric allylic cycloaddition of vinyloxetanes with an abundant feedstock, formaldehyde, is developed. Using the palladium complex generated in situ from Pd2(dba)3·CHCl3 and phosphoramidite L3 as a catalyst under mild conditions, the process allows one to convert racemic 2-substituted 2-vinyloxetanes (1) to the corresponding 1,3-dioxanes (2) as methylene acetal protected tertiary 1,3-diols in high yields with good to excellent enantioselectivities.