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Ring‐opening of Epoxides Mediated by Frustrated Lewis Pairs
Author(s) -
Krachko Tetiana,
Nicolas Emmanuel,
Ehlers Andreas W.,
Nieger Martin,
Slootweg J. Chris
Publication year - 2018
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.201801909
Subject(s) - frustrated lewis pair , chemistry , borane , epoxide , lewis acids and bases , moiety , ring (chemistry) , stereochemistry , nucleophile , catechol , medicinal chemistry , catalysis , organic chemistry
Treatment of the preorganized frustrated Lewis pairs (FLPs) t Bu 2 PCH 2 BPh 2 ( 1 ) and o ‐Ph 2 P(C 6 H 4 )BCat (Cat=catechol) ( 4 ) with 2‐methyloxirane, 2‐phenyloxirane and 2‐(trifluoromethyl)oxirane resulted in epoxide ring‐opening to yield the six‐ and seven‐membered heterocycles 2 a – c and 5 a – c , respectively. These zwitterionic products were characterized spectroscopically, and compounds 2 a , 2 b , 5 a and 5 c were structurally characterized by single‐crystal X‐ray structure analyses. Based on computational and kinetic studies, the mechanism of these reactions was found to proceed via activation of the epoxide by the Lewis acidic borane moiety followed by nucleophilic attack of the phosphine of a second FLP molecule. The resulting chain‐like intermediates afford the final cyclic products by ring‐closure and concurrent release of the second equivalent of FLP that behaves as catalyst in this reaction.