Selective Double Carbomagnesiation of Internal Alkynes Catalyzed by Iron-N-Heterocyclic Carbene Complexes: A Convenient Method to Highly Substituted 1,3-Dienyl Magnesium Reagents.
J Am Chem Soc
; 138(1): 112-5, 2016 Jan 13.
Article
in En
| MEDLINE
| ID: mdl-26713433
ABSTRACT
Controlled multicarbometalation of alkynes has been envisaged as an efficient synthetic method for dienyl and polyenyl metal reagents, but an effective catalyst enabling the transformation has remained elusive. Herein, we report that an iron(II)-N-heterocyclic carbene (NHC) complex (IEt2Me2)2FeCl2 (IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene) can serve as a precatalyst for the double carbometalation of internal unsymmetrical alkynes with alkyl Grignard reagents, producing highly substituted 1,3-dienyl magnesium reagents with high regio- and stereoselectivity. Mechanistic studies suggest the involvement of low-coordinate organoiron(II)-NHC species as the in-cycle intermediates. The strong σ-donating nature of IEt2Me2 and its appropriate steric property are thought the key factors endowing the iron-NHC catalyst fine performance.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
J Am Chem Soc
Year:
2016
Document type:
Article