1.School of Chemistry and Materials Science,Shanxi Normal University,Linfen,China
Abstract:
The mechanism of phenanthridines synthesis from the nitrogenation of 2-acetylbiphenyls (1) by TMSN3 in TFA has been studied by DFT calculations. Results at the B3LYP/6-311G(d) level showed that: 1) reaction of TMSN3/HN3 with the protonated form of 1 (1H+), which generates the key intermediate Cx+ by removal of TMSOH/H2O, is the rate determining step, and TMSN3 as the nitrogen source is certainly preferred over HN3. 2) from Cx+, the two pathways leading to 2xH+ and 3xH+ are both thermodynamically and kinetically feasible and competitive to each other. 3) The high barriers of the reverse reactions suggest that the ratio of the final products 2x:3x is determined by the branching ratio of reaction rates of Cx+ to intermediates Dx+ in pass_I and Ex+ in pass_II.
Graphical Abstract DFT results indicate that the replacement of -OH by -N3 which generates Cx+ controls the consumption rate of 1x H+, and the ratio of Cx+ transforms to Dx+ and Cx+ transforms to Ex+ (k:k') determines the final ratio of products 2x:3x.