February 3, 2015

Competition studies and the relative reactivity of enol ether and allylsilane coupling partners toward ketene dithioacetal derived radical cations

Campbell, John M.; Smith, Jake A.; Gonzalez, Luisalberto and Moeller, Kevin D.

Tetrahedron Letters, 2015Ahead of Print

The relative reactivity of enol ether and allylsilane trapping groups toward a ketene dithioacetal derived radical cation has been examd. with the use of competition and cyclic voltammetry studies.  The competition studies pit the olefinic trapping groups against an alc. trapping group under conditions of both kinetic and thermodn. control.  With the enol ether trapping group, the chemoselectivity of the competition study favored C-​C bond formation under all conditions.  With the allylsilane trapping group, the chemoselectivity of the competition study favored C-​O bond formation under all conditions.  Cyclic voltammetry data was used to show that allylsilane trapping of the radical cation is much slower than enol ether trapping of the radical cation.  However, the inefficiency of the allylsilane trapping reaction could not be attributed solely to a slow cyclization.  Rather, it appears that a slow second oxidn. step plays a role in detg. the yield of the reaction.