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Cyclisation versus 1,1‐Carboboration: Reactions of B(C 6 F 5 ) 3 with Propargyl Amides
Author(s) -
Melen Rebecca L.,
Hansmann Max M.,
Lough Alan J.,
Hashmi A. Stephen K.,
Stephan Douglas W.
Publication year - 2013
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.201301899
Subject(s) - propargyl , chemistry , physics , medicinal chemistry , catalysis , organic chemistry
A series of propargyl amides were prepared and their reactions with the Lewis acidic compound B(C 6 F 5 ) 3 were investigated. These reactions were shown to afford novel heterocycles under mild conditions. The reaction of a variety of N ‐substituted propargyl amides with B(C 6 F 5 ) 3 led to an intramolecular oxo‐boration cyclisation reaction, which afforded the 5‐alkylidene‐4,5‐dihydrooxazolium borate species. Secondary propargyl amides gave oxazoles in B(C 6 F 5 ) 3 mediated (catalytic) cyclisation reactions. In the special case of disubstitution adjacent to the nitrogen atom, 1,1‐carboboration is favoured as a result of the increased steric hindrance (1,3‐allylic strain) in the 5‐alkylidene‐4,5‐dihydrooxazolium borate species.