Synthesis of hindered functionalized ethers via high-pressure addition of alcohols to acrylic compounds

The phosphine-catalyzed 1.4-addition of alcohols to activated alkenes is studied from a synthetic point of view. alpha- or beta -Subsiituted acrylic compounds react sluggishly or not at all. In this case, high-pressure activation can remove steric inhibition leading to good yields of the corresponding beta ethers. Reactions involving crotonic compounds (hindered reaction center) show higher pressure dependence than the corresponding additions of alcohols to methacrylic analogs (free beta reaction center). This is in agreement with the concept that sterically demanding reactions show enhanced sensitivity to pressure. The result, obviously, is of high synthetic value as pressure may be capable of removing steric inhibition. (C) 2001 Elsevier Science Ltd. All rights reserved.