Chiral 1,2-Diols via One-Pot Diboration/Hydroboration/Cross-Coupling

Significance

The described sequence allowed the enantioselective preparation of syn-1,2-diols from simple allene starting materials in one pot. In the case where vinyl halides (R²-X) are used in the carbon-carbon coupling reaction, the products obtained (4) are chiral homoallylic diols. These compounds would be difficult to obtain with classic dihydroxylation methods. Impressively, the Pd catalyst was still active after steps i) and ii), which required 26 h in total, and the Suzuki reaction was selective for the terminal borane. As the overall yield (generally around 50%) represents four distinct reactions, the average yield is ˜92% for each step. The enantio­selectivity was reliably high, regardless of the allene substituent R¹.