Multi-Pathway Consequent Chemoselectivities of CpRuCl(PPh₃ )₂ /MeI-Catalysed Norbornadiene Alkyne Cycloadditions.

ABSTRACT: Chemoselectivities of five experimentally realised CpRuCl(PPh₃ )₂ /MeI-catalysed couplings of 7-azabenzo-norbornadienes with selected alkynes were successfully resolved from multiple reaction pathway models. Density functional theory calculations showed the following mechanistic succession to be energetically plausible: (1)?CpRuI catalyst activation; (2)?formation of crucial metallacyclopentene intermediate; (3)?cyclobutene product (P2) elimination (?G_Rel(RDS) ?11.9-17.6?kcal?mol^-1 ). Alternative formation of dihydrobenzoindole products (P1) by isomerisation to azametalla-cyclohexene followed by subsequent CpRuI release was much less favourable (?G_Rel(RDS) ?26.5-29.8?kcal?mol^-1 ). Emergent stereoselectivities were in close agreement with experimental results for reactions a, b, e. Consequent investigations employing dispersion corrections similarly support the empirical findings of P1 dominating in reactions c and d through P2?P1 product transformations as being probable (?G?25.3-30.1?kcal?mol^-1 ).

SUBMITTER: Mu WH 

PROVIDER: S-EPMC5082545 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature