Production of Formamides from CO and Amines Induced by Porphyrin Rhodium(II) Metalloradical

It
is of fundamental importance to transform carbon monoxide (CO)
to petrochemical feedstocks and fine chemicals. Many strategies built
on the activation of CO bond by π-back bonding from
the transition metal center were developed during the past decades.
Herein, a new CO activation method, in which the CO was converted
to the active acyl-like metalloradical, [(por)­Rh­(CO)]• (por = porphyrin), was reported. The reactivity of [(por)­Rh­(CO)]• and other rhodium porphyrin compounds, such as (por)­RhCHO
and (por)­RhC­(O)­NHnPr, and corresponding
mechanism studies were conducted experimentally and computationally
and inspired the design of a new conversion system featuring 100%
atom economy that promotes carbonylation of amines to formamides using
porphyrin rhodium­(II) metalloradical. Following this radical based
pathway, the carbonylations of a series of primary and secondary aliphatic
amines were examined, and turnover numbers up to 224 were obtained.