Copper-Catalyzed Decarboxylative Radical Silylation of Redox-Active Aliphatic Carboxylic Acid Derivatives

A decarboxylative silylation of aliphatic N-hydroxyphthalimide (NHPI) esters using Si-B reagents as silicon pronucleophiles is reported. This C(sp³ )-Si cross-coupling is catalyzed by copper(I) and follows a radical mechanism, even with exclusion of light. Both primary and secondary alkyl groups couple effectively, whereas tertiary alkyl groups are probably too sterically hindered. The functional-group tolerance is generally excellent, and α-heteroatom-substituted substrates also participate well. This enables, for example, the synthesis of α-silylated amines starting from NHPI esters derived from α-amino acids. The new method extends the still limited number of C(sp³ )-Si cross-couplings of unactivated alkyl electrophiles.