Theoretical analysis of pyrrole anions addition to carbon disulfide and carbon dioxide

Quantum chemical analysis (MP2/6-31+G*) of the pyrrole anions addition to carbon disulfide and the substitution effects therein shows that pyrrole-2 (5)-carbodithioates are thermodynamically the most stable compounds, while 1-isomer obtained from the unsubstituted pyrrole is likely a kinetic product. Steric hindrances destabilize N-adducts when a methyl substituent appears in a 2(5) position and the 2,5-dimethyl-1-pyrrolecarbodithioate anion turns out to be even less stable than the 2,5-dimethyl-3-pyrrolecarbodithioate anion. By contrast, pyrrole-1-carboxylates are calculated to be the most stable adducts of CO2 with pyrrole anions. (C) 2002 Wiley Periodicals, Inc.