Factors influencing 1,4-asymmetric induction during indium-promoted coupling of oxygen-substituted allylic bromides to aldehydes in aqueous solution

摘要

The preparation and indium-promoted aldehyde addition reactions of a series of 3-substituted 3-oxy- 1- bromo-2-methylidenepropanes under aqueous conditions are described. The (tert-butyldimeth- ylsilyl)oxy deivatives 4a-d are the most diastereoselective of this group of reagnts, giving rise to levels of syn-1,4-asymmetric induction in the range of 87-99/100. Interestingly, syn stereoselectivity is eroded and reactions proceed more rapidly when the steric bulk of the oxygen substituent is reduced as in the hydroxy and methoxy derivatives.