Stabilized carbanions Henry reaction

Additions of stabilized carbanions to imines and hydrazones, respectively, have been used to initiate domino 1,2-addition/cyclization reactions. Thus, as described by Benetti and coworkers, 2-subshtuted 3-nitropyrrolidines are accessible via a nitro-Mannich (aza-Henry)/SN-type process [165]. Enders research group established a 1,2-addition/lactamization sequence using their well-known SAMP/ RAMP-hydrazones 2-308 and lithiated o-toluamides 2-307 as substrates to afford the lactams 2-309 in excellent diastereoselectivity (Scheme 2.72) [166]. These compounds can be further transformed into valuable, almost enantiopure, dihydro-2H-isoquinolin-l-ones, as well as dihydro- and tetrahydroisoquinolines. 

The utilization of carbanions stabilized by various electron-withdrawing groups to effect carbon-carbon bond formation occupies a central position in organic synthesis. This chapter focuses on the reactions of nitro-stabilized carbanions (nitronate anions or their equivalents) with aldehydes and ketones. This route for the coupling of a carbonyl and a nitroalkane component, leading to vicinal nitro alcohols, was discovered in 1895 by Henry and is currently known as the Henry or nitroaldol reaction. 

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