H· Transfer-Initiated Synthesis of γ‑Lactams: Interpretation of Cycloisomerization and Hydrogenation Ratios

A cobaloxime/H2 system
used to synthesize valuable γ-lactams
from acrylamide molecules is described. In addition to cycloisomerized
lactams, linear hydrogenated products were also observed. The amounts
of the hydrogenation product were observed to correlate with the bulk
of the substituent on the acrylamide nitrogen. Further analysis of
the product distributions with experimental and computational studies
suggested that while cyclization can occur from one CC acrylamide
rotamer, hydrogenation can occur from both. This observation was further
evinced through calculation of the hydrogenation rate constant, which
was observed to be ca. 102 faster than previously determined
for a related system using nBu3SnH.