The dimesitylboron group in organic synthesis 7. A unique variant of the Boron-Wittig reaction which stereoselectively yields 1,2-diols

Low temperature oxidation of the intermediates in the Wittig reactions of aryl aldehydes with carbanions stabilised with an adjacent dimesitylboron group leads stereo-selectively to $\text{erythro}$-1,2-diols. The mechanistic implications for the boron-Wittig reactions are discussed.