A process for protecting aldehydes and ketones in crossed aldol condensations where both aldols possess alpha-carbon hydrogens, comprising protecting the target aldol by forming an acetal or imine with an alcohol, glycol or primary amine which may contain electron-withdrawing groups, adding a base of sufficient strength to abstract a proton from the alpha-carbon of the acetal or imine and adding the second aldol to form the salt of the saturated hydroxy addition compound, thereby minimizing by-products, waste and separation difficulties, then forming the unsaturated addition compound and decomposing the acetal or imine with dilute acid. This process having the advantage that a ketone may be added to a protected aldehyde target to produce an aldehyde as a product which was not previously possible.
在交叉的醛
缩醛反应中保护醛和酮的过程,其中两种醛都具有α-碳氢,包括通过与醇、
乙二醇或含有电子吸引基团的初级胺形成
缩醛或
亚胺来保护目标醛,加入足够强度的碱来从
缩醛或
亚胺的α-碳中提取质子,并加入第二个醛以形成饱和羟基加成化合物的盐,从而最小化副产物、废物和分离困难,然后形成不饱和加成化合物并用稀酸分解
缩醛或
亚胺。这个过程的优点是可以将酮添加到受保护的醛目标中,从而产生一种以前不可能的醛作为产物。