Highly Discriminative and Chemoselective Deprotection/Transformations of Acetals with the Combination of Trialkylsilyl Triflate/2,4,6-Collidine

Acetals
are the most useful protecting groups for carbonyl functional
groups. In addition to the role of protection, they can also be used
as synthons of carbonyl functions. Previously, we developed a chemoselective
deprotection and nucleophilic substitution of acetals from aldehydes
in the presence of ketals. This article describes the highly discriminative
and chemoselective transformations of acetals bearing different substitution
patterns, different types of acetals, as well as mixed acetals. These
reactions can achieve the transformations that cannot be attained
by conventional methods, and their results strongly suggest the combination
of R3SiOTf/2,4,6-collidine to promote such unprecedented
phenomena.