Facile, green, and functional group-tolerant reductions of carboxylic acids horizontal ellipsis in, or with, water

Facile reductions of carboxylic acids to aldehydes or alcohols can be effected under mild conditions upon initial conversion to their corresponding S-2-pyridyl thioesters. Upon treatment with a commercially available and air-stable nickel pre-catalyst and silane as a stoichiometric reductant, aldehydes are formed in moderate to good yields. Alternatively, the 1-pot conversion of acids to their thioester derivatives can be followed by reduction to the alcohol upon treatment with sodium borohydride. A variety of starting materials ranging from highly functionalized acids to educts from the Merck informer library can be transformed using these green reaction media.