Benzotriazole-stabilized carbanions

Michael additions of benzotriazole-stabilized carbanions 98CCC599. Properties and synthetic utility of N-substituted benzotriazoles 98CRV409. 

Michael Additions of Benzotriazole-Stabilized Carbanions <1998CCC599> ... 

Michael additions to benzotriazole-stabilized carbanions have been reviewed. review of the structural dependence of heterolytic bond dissociation energy of carbon-carbon a-bonds in hydrocarbons has summarized the synthesis and behaviour of molecules in which highly stable cationic and anionic hydrocarbon moieties have apparently been combined. 

During the coverage period of this chapter, reviews have appeared on the following topics reactions of electrophiles with polyfluorinated alkenes, the mechanisms of intramolecular hydroacylation and hydrosilylation, Prins reaction (reviewed and redefined), synthesis of esters of /3-amino acids by Michael addition of amines and metal amides to esters of a,/3-unsaturated carboxylic acids," the 1,4-addition of benzotriazole-stabilized carbanions to Michael acceptors, control of asymmetry in Michael additions via the use of nucleophiles bearing chiral centres, a-unsaturated systems with the chirality at the y-position, and the presence of chiral ligands or other chiral mediators, syntheses of carbo- and hetero-cyclic compounds via Michael addition of enolates and activated phenols, respectively, to o ,jS-unsaturated nitriles, and transition metal catalysis of the Michael addition of 1,3-dicarbonyl compounds. ... 

Katritzky, A. R., Qi, M. Michael additions of benzotriazole-stabilized carbanions. A review. Collect. Czech. Chem. Common. 1998, 63, 599-613. 

Review topics have included three-carbon homologations employing benzotriazole-stabilized allylic anions,and recent synthetic applications of aza-allyl carbanions derived from a-amino acid derivatives. ... 

LDA). Furthermore, Katrizky and coworkers have achieved highly stereoselective synthesis of -stilbene by reaction of tosylhydrazones with benzotriazole-stabilized carbanion with the aid of organolithium [32,33] - see (5) - X = 1 -benzotriazolyl (Bt). This method can be compared with Julia-type olefination, in which aldehyde is the substrate in the place of tosylhydrazone. 

The chemistry of benzotriazole has been developed to the point where it has now found extensive use for heterocyclic and general synthesis, A useful set of properties give it this role (i) a-carbanions are stabilised to the same extent as at the benzylic position of a benzene compound (ii) a-carbocations are also stabilised (iii) the benzotriazolyl anion is also a good leaving group with a combination of good reactivity and stability/ease of handling. Sequential combinations of these reactivities have been applied to the synthesis of a wide variety of molecules - some illustrative examples are shown below. 

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