Heterocumulenes Reactions with Organometallic Reagents: XXI.* Quantum-Chemical Study of Structural Transformations of 2-Methoxy- and 2-(Methylsulfanyl)-N-methylbuta-2,3-dienimidothioates in the Presence of CuBr: Pyrrole or Methyl-3-(methylsulfanyl)but-2-enimidothioate?

摘要

Utilizing the MP2/6-31G(d,p) method a quantum-chemical investigation was performed of processes catalyzed by CuBr leading to the formation of pyrrole structures from methyl-2 methoxy- and methyl 2-(methylsulfanyl)-N-methylbuta-2,3-dienimidothioates (1-aza-1,3,4-trienes). According to calculations 1-aza-1,3,4-trienes may form highly stable adducts with CuBr owing to the coordination bonding of the copper atom with the re-system (C=C=C) and/or heteroatoms (N, S, O). The main channel of the structural reorganization of the CuBr adduct with methoxy-substituted 1-aza-1,3,4-triene is the thermodynamically controlled formation of the pyrrole ring. In the 3-(methylsulfanyl)-1-aza-1,3,4-triene CuBr initiates the cleavage of the C-S bond in the imidothioate fragment (MeS-C=N-Me) and the kinetically controlled formation of methyl N-methyl-2,3-bis(methylsulfanyl) but-2-enimidothioate.