Enolate Equivalents from a,p-unsaturated Aldehydes

Combined with their previously developed NHC-catalyzed asymmetric Michael reaction, the Scheidt group reported an enantioselective synthesis 

2 Enolate Equivalents from Aldehydes with an o-Leaving Group 

In 2014, Huang, Zhong, and co-workers delivered an NHC-catalyzed enan-tioselective aza-Diels-Alder reaction of oxodiazenes with a-chloroaldehydes 

Seheme 7.83 NHC-catalyzed asymmetric a-amination of a-chloroaldehydes and oxodiazenes reported by Smith. 

In 2010, Rovis and co-workers reported a related reaction providing a-halocarboxylic acids from o,a-dihaloaldehydes or a-fluoroenals in good yields and excellent enantioselectivity (up to 95% yield and 96% ee). Buffered, biphasie aqueous conditions were employed to overeome the problem of epimerization and achieve high seleetivity (Seheme 7.86). 

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