Generation and cycloaddition of semi-stabilized 2-azaallyllithiums via electrocyclic ring-opening or cycloreversion reactions

Abstract

Semi-stabilized 2-azaallyl anions, i.e., those bearing aryl groups, have been generated by either the electrocyclic ring-opening of N-lithioaziridines or the 1,3-anionic cycloreversion of N-lithioimidazolidines.

Modification and Unexpected Reactivity of 2-Borylbenzaldimines: Acylated and Silylated Derivatives as Well as Dimeric Compounds

“…As the spectroscopic and crystallographic data indicate, compound 6 unexpectedly adopts a dimeric structure . The proton NMR spectrum of 6 shows the characteristic signal for the CH 2 group of the saturated B/N heterocycle as a singlet at 4.44 ppm (Figure ).…”

Tandem [3 + 2] Cycloaddition/1,4-Addition Reaction of Azomethine Ylides and Aza-o-quinone Methides for Asymmetric Synthesis of Imidazolidines

“…In sharp contrast, due to the lower reactivity of imines, enantioselective 1,3-DCs of azomethine ylides with carbon–nitrogen double bonds are rare . The key reason for this situation is that the 1,3-DCs of azomethine ylides with imines might be reversible, , thus leading to low yields of the imidazolidines. Capturing imidazolidines in situ will be a good strategy to drive the reaction to completion for efficient construction of the chiral imidazolidine skeleton, which constitutes the core structure of many natural products, bioactive compounds, and important catalysts or ligands …”

Highly stereoselective construction of novel dispirooxindole–imidazolidines via self-1,3-dipolar cyclization of ketimines

“…[33][34][35][36] However, limited progress has been made in this area ever since. [37][38][39][40][41][42] In 2002, Pearson and coworkers observed that the deprotonation of aldimines using LDA afforded self-1,3-dipolar cycloadducts in unsatisfactory yield and regioselectivity. 39 Thereafter, Cossío reported an unusual [3 + 2] autocyclization of an aldimine derived from an aromatic aldehyde and a glycine methyl ester in the presence of AgClO 4 , providing the corresponding imidazolidine in poor to moderate yields, albeit with high diastereoselectivity.…”