摘要:
The free-radical hydrostannation of 1 with Ph3SnH and catalytic Et3B in PhMe has been mechanistically probed. At high Ph3SnH concentrations, the O-directed hydrostannation pathway dominates, and 2 is formed with good selectivity (ca. 11.1:1). Substantially lower stannane/substrate concentrations increase the amount of tandem 5-exo-trig cyclization product 3 that is observed.