N-Heterocyclic carbens in organocatalysis

Ξ August 10th, 2008 | → 2 Comments | ∇ N-Heterocyclic Carbens |

 Direct Amination of Homoenolates Catalyzed by

N-Heterocyclic Carbens

J. Am. Chem. Soc. 2008, 130, 2740-2741


 

 

The construction of C - N bonds is a very important goal in organic chemistry. Here I report a JACS paper about the development of a catalytic amination of homoenolates by combining α,β-unsatured aldehydes with diazenes in the presence of N-Heterocyclic carbens.

 

Below I report the general reactioon. 

 

The reaction mechanism is showed below.

 

 

 

First we have the addition of an NHC to unsatured aldehyde, to afford the tetrahedral intermediate A. 

Upon rearrangement, the diene homoenolate B is generated which undergoes addition to diazene C and subsequently generates ketone D after tautomerization. This activated carbonyl species facilities catalyst turnover by intramolecular acylation to produce pyrazolidinone.