The SYNTHESIS OF Α-Halogenated IMINO COMPOUNDS

1-Azaallylic Anions in Heterocyclic Chemistry

“…Another example of regioselective deprotonation of imines is given by the use of 3-halo-1-azaallylic anions 15 (X = Cl, Br, F) . In particular, treating α-chloroimines 14 (X = Cl) with lithium bases at 0 °C (or −78 °C) in THF smoothly results in the regiospecific deprotonation at the more acidic α-carbon (Scheme ). , The previously mentioned 3-halo-1-azaallylic anions represent attractive building blocks in the generation of heterocycle systems (vide infra).…”

Highly Regioselective Transformation of Alkenyl Bromides into α-Bromoaziridines and α-Bromohydrazones

“…The most common methods of α-haloimine or α-halohydrazone synthesis are α-halogenation of imines or hydrazones and condensation of α-halogenated carbonyl compounds with primary amines hydrazines. The condensation pathway proceeds with low chemoselectivity, plagued by side-reactions such as nucleophilic substitution of α-halogen, base-promoted elimination of hydrogen halide, Favorskii rearrangement, and formation of epoxide intermediates . In turn, imine and hydrazone halogenation suffers from poor regio- and chemoselectivity, affording mixtures of mono- and dihalogenated compounds .…”

“…The condensation pathway proceeds with low chemoselectivity, plagued by side-reactions such as nucleophilic substitution of α-halogen, base-promoted elimination of hydrogen halide, Favorskii rearrangement, and formation of epoxide intermediates . In turn, imine and hydrazone halogenation suffers from poor regio- and chemoselectivity, affording mixtures of mono- and dihalogenated compounds . Herein, we report a novel route to α-bromoaziridines 2 and their rearrangement into α-bromohydrazones 3 (Scheme ).…”

Asymmetric synthesis of γ-chloro-α,β-diamino- and β,γ-aziridino-α-aminoacylpyrrolidines and -piperidines via stereoselective Mannich-type additions of N-(diphenylmethylene)glycinamides across α-chloro-N-sulfinylimines

“…The synthesis of chiral α,β-diaminocarboxylic acid derivatives by asymmetric Mannich-type addition of enolates across activated imines, e.g., N -sulfinylimines [16–20], is one of the most common and versatile methods in organic chemistry and is continuously under development [1–3]. Recently, our research group elaborated the asymmetric synthesis of new chiral γ-chloro-α,β-diaminocarboxyl esters by highly diastereoselective Mannich-type reactions of N -(diphenylmethylene)glycine esters across a chiral α-chloro- N - p -toluenesulfinylimine [20], which belongs to the useful class of α-halo-imines [21–26]. However, transformation of γ-chloro-α,β-diaminocarboxyl esters into the corresponding carboxylic acids, en route to further coupling to carboxylamides, has proven to be unsuccessful, probably due to competitive reactions such as the formation of α,β-diamino-γ-butyrolactones [20].…”