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Multi‐Pathway Consequent Chemoselectivities of CpRuCl(PPh 3 ) 2 /MeI‐Catalysed Norbornadiene Alkyne Cycloadditions
Author(s) -
Mu WeiHua,
Fang DeCai,
Xia ShuYa,
Cheng RuiJiao,
Chass Gregory A.
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201603173
Subject(s) - norbornadiene , cyclobutene , isomerization , chemistry , catalysis , density functional theory , alkyne , cycloaddition , cyclohexene , medicinal chemistry , computational chemistry , photochemistry , organic chemistry , ring (chemistry)
Chemoselectivities of five experimentally realised CpRuCl(PPh 3 ) 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 (Δ 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 (Δ 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 (Δ G ≈25.3–30.1 kcal mol −1 ).