Benzotriazolyl leaving group

The first report of direct carbanion formation by acyclic C—N bond cleavage has exploited the benzotriazolyl leaving group in a novel transformation promoted by lithium in THF (Scheme ll).176... 

The benzotriazolyl group is a good leaving group. This feature was exploited in the use of benzotriazolylmethyl-aminomethyltrimethylsilane as a precursor of an azomethine ylid. At reflux in toluene, benzotriazolyltrimethylsilane was eliminated and formation of the ylid underwent quantitative [l,3]dipolar cycloaddition with diethyl fumarate, for example, giving a frans-3,4-dicarboethoxy pyrrolidine derivative exclusively. Other examples were reported as well.442... 

Heterocycles Containing More Than Two Heteroatoms 573 Benzotriazolyl is a useful leaving group for nucleophilic substitutions in 1,2,3-thiadiazoles. ... 

The benzotriazolyl anion is an excellent leaving group therefore, benzotriazole derivatives have been used extensively as precursors of synthetic components. Furthermore, these reagents are readily obtained from equimolar benzotriazole, an aldehyde, and a secondary amine. A review of synthetic uses of benzotriazole derivatives appeared in 1991. 

Diarylcyclopropylphenyl sulfides. The cyclopropanation takes place when the reagent is deprotonated with LDA in the presence of 1,1-diarylethene. Benzotria-zole acts as a leaving group in the ring-closure step. Simpler benzotriazolyl derivatives also undergo the same reaction. 

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. 

Used for pptn. separation and gravimetric detn. of Cd, Co, Ni, Zn. The benzotriazolyl group is an extremely versatile substituent showing props, of leaving group, electron donor and ability to promote adjacent proton loss. Needles (C H ). Sol. C H. Mp 100°. 1.6 ... 

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