2-Benzotriazolylaziridines and Their Reactions with Diethyl Acetylenedicarboxylate

1-(2H-Azirine-2-carbonyl)benzotriazoles: building blocks for the synthesis of pyrrole-containing heterocycles

A one-pot method was developed for the preparation of 2H-azirine-2-carbonylbenzotriazoles, formed by the reaction of benzotriazole with 2H-azirine-2-carbonyl chlorides, which were generated by the Fe(ii)-catalyzed isomerization of 5-chloroisoxazoles. The Co(ii)-catalyzed reaction of 2H-azirine-2-carbonylbenzotriazoles with 1,3-diketones provides 2-((benzotriazol-1-yl)carbonyl)pyrroles in moderate to good yields. Base-promoted annulations of 2-((benzotriazol-1-yl)carbonyl)pyrroles with aldehydes, ketones, isocyanates and isothiocyanates afford various substituted pyrrolo[1,2-c]oxazole and 1H-pyrrolo[1,2-c]imidazole derivatives in moderate to high yields. The 6-acyl group of these adducts can be removed by triflic acid, giving further new pyrrolo-fused O- and N-heterocycles, such as 6-unsubstituted pyrrolo[1,2-c]oxazol-1(3H)-one and 1H-pyrrolo[1,2-c]imidazole-1,3(2H)-dione, while the 6-acetyl substituent of 1H-pyrrolo[1,2-c]imidazole-1,3(2H)-dione, when treated with POCl3/pyridine, is transformed into the 6-ethynyl substituent.

Lewis acid-catalyzed [3 + 2]cyclo-addition of alkynes with N-tosyl-aziridines via carbon-carbon bond cleavage: synthesis of highly substituted 3-pyrrolines

A novel, efficient, and highly regioselective Lewis acid-catalyzed [3 + 2] cycloaddition of alkynes with azomethine ylides, which are easily obtained from N-tosylaziridines via C-C bond heterolysis at room temperature was developed. Moderate enantioselectivity (70% ee) can be achieved by the application of the commercially available chiral Pybox 7 as the ligand.

1,2,3-Triazoles

Rapid progress in the synthetic application of benzotriazole derivatives in the last 20 years has resulted in over 1000 scientific papers on the subject. This fact is reflected in Section 5.01.7, which involves almost a half of the volume of this chapter. The section is arranged according to hybridization of the C-α atom and atomic numbers of the atoms in positions β and γ to allow an easy access to the material of interest. Recent discovery of copper catalysis in [3+2] cycloadditions of azides to acetylenes, the so-called ‘click chemistry’, which boosted application of the 1,2,3-triazole derivatives, especially in medicinal chemistry, is presented in Section 5.01.9. From the point of view of practical applications, Section 5.01.11 is organized according to the number, position, and combination of the substituents at the aromatic rings. Another novel feature that has no precedence in the previous editions of Comprehensive Heterocyclic Chemistry is an addition of triazole and benzotriazole complexes with various transitions metals to Section 5.01.4.

Stereoselective Functionalization of 2-(1-Aminoalkyl)aziridines via Lithiation of Aziridine-Borane Complexes

Highly selective functionalization of the aziridine ring of (2S,1'S)-2-(1'-aminoalkyl)aziridines 1, through successive formation of aziridine-borane complexes, lithiation, treatment with a variety of electrophiles and final decomplexation is described. The influence of the structure of the starting complexes 2 and of the electrophiles in the stereoselectivity of this process has been studied. Finally, successive double lithiation-electrophile reactions were carried out affording enantiopure 1,2,3,3-tetrasubstituted aziridine-borane complexes with high selectivity.

Aziridinyl anions from a chiral, nonracemic 2-isopropylidineaziridine: surprisingly diastereoselective alkylation reactions

Lithiation and alkylation of a 2-isopropylidineaziridine bearing an (S)-alpha-methylbenzyl group on nitrogen proceeds with high levels of diastereocontrol (80-90% de).

Lithiation of 1-chloromethylbenzotriazole: generation and elaboration of benzotriazolyloxiranes

1-Benzotriazolylchloromethyllithium generated from 1-chloromethylbenzotriazole (1) and LDA reacts with enolizable and nonenolizable ketones to give benzotriazolyloxiranes 2a-g in good yields. The oxiranyllithiums 4a-d generated from 2a-d and n-BuLi at -78 degrees C were trapped by a variety of electrophiles to give oxiranyl derivatives 5a-j in good to excellent yields. Lewis-acid-promoted nucleophilic ring opening of benzotriazolyloxiranes 2a,f,g with allyltrimethylsilane gave the corresponding 1,7-octadien-4-ols 6a-c in 68-75% yield. Hydrolysis of alpha-acylbenzotriazolyloxiranes 5g,h provided 3-hydroxy-1,2-diones 7a and 7b in 73 and 86% yield, respectively.