Table 1.

Selected optimization by screening influences of boronic acid catalysts and chiral ligands

Conditions: [a] Polyol 15a (0.1 mmol), 16a (0.2 mmol), Rh(cod)₂OTf (5 mol%), ligand (6 mol%), organoboron catalyst (30 mol%), in THF (1 ml), argon, 50 °C, 24 h. Screening of boronic acid catalyst achieved with L12 and screening of ligand achieved with boronic acid 26. [b] Yields and r.r. (C3:C2) ratio were determined by analysis of the crude ¹H NMR spectra obtained using 1,3,5-trimethoxybenzene as an internal standard. [c] Polyol 15a (0.2 mmol), 16a (0.4 mmol), Rh(cod)₂OTf (5 mol%), ligand (6 mol%), organoboron catalyst (30 mol%), in THF (2 ml), argon, 50 °C, 24 h. [d] Isolated yields. cod, 1,5-cyclooctadiene; TBS, tert-butyldimethylsilyl.