Brønsted Acid-Catalyzed Cyanotritylation of Aldehydes by Trityl Isocyanide

Cyanohydrins are
versatile intermediates toward valuable organic
compounds like α-hydroxy carboxylic acids, α-amino acids,
and β-amino alcohols. Numerous protocols are available for synthesis
of (O-protected) cyanohydrins, but all procedures invariably rely
on the use of toxic cyanide sources. A novel cyanide-free synthesis
of O-trityl protected cyanohydrins via a catalytic
Passerini-type reaction involving aldehydes and trityl isocyanide
is reported. The feasibility of a catalytic asymmetric reaction is
demonstrated using chiral phosphoric acid catalysis.