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Characterization of the Zwitterionic Intermediate in 1,1‐Carboboration of Alkynes
Author(s) -
Bismuto Alessandro,
Nichol Gary S.,
Duarte Fernanda,
Cowley Michael J.,
Thomas Stephen P.
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202003468
Subject(s) - alkyne , zwitterion , chemistry , reactivity (psychology) , borane , substituent , intramolecular force , ferrocene , medicinal chemistry , catalysis , combinatorial chemistry , stereochemistry , organic chemistry , molecule , medicine , alternative medicine , electrode , pathology , electrochemistry
The reaction of a Lewis acidic borane with an alkyne is a key step in a diverse range of main group transformations. Alkyne 1,1‐carboboration, the Wrackmeyer reaction, is an archetypal transformation of this kind. 1,1‐Carboboration has been proposed to proceed through a zwitterionic intermediate. We report the isolation and spectroscopic, structural and computational characterization of the zwitterionic intermediates generated by reaction of B(C 6 F 5 ) 3 with alkynes. The stepwise reactivity of the zwitterion provides new mechanistic insight for 1,1‐carboboration and wider B(C 6 F 5 ) 3 catalysis. Making use of intramolecular stabilization by a ferrocene substituent, we have characterized the zwitterionic intermediate in the solid state and diverted reactivity towards alkyne cyclotrimerization.