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Mechanistic Understanding of Alkyne Haloboration: An Ab Initio Study
Author(s) -
Wang Chao,
Uchiyama Masanobu
Publication year - 2012
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201200975
Subject(s) - chemistry , isomerization , halide , alkyne , computational chemistry , ab initio , metalation , boron , catalysis , ab initio quantum chemistry methods , transition state , photochemistry , organic chemistry , molecule
Ab initio calculations have been performed with second‐order Møller–Plesset perturbation theory (MP2) to understand the mechanisms of alkyne haloboration. The present study throws light on three important aspects of this reaction: (1) reaction routes, (2) stereoconversion pathways, and (3) physicochemical uniqueness. The cis ‐Markovnikov reaction route is controlled by a characteristic four‐centered transition state, reflecting the roles of alkynes and boron halides, and also the stability of the product. For the stereoconversion pathways, a boron‐halide‐mediated addition–elimination process appears to be most favorable. Nevertheless, the high activation barrier suggests that prolonged heating with excess boron halide (commonly used in synthesis) would favor cis / trans isomerization. Finally, comparison with other halometalations showed clear thermodynamic and kinetic advantages of haloboration as a unique, catalyst‐free protocol among many elemento‐metalation reactions.