Microwave-assisted synthesis of Nitroketene N,S-Arylaminoacetals

Abstract

Neste trabalho nós relatamos o uso de microondas como fonte de energia para promover a síntese de uma série de nitroeteno N,S-acetais com bons rendimentos. Estes compostos são intermediários muito úteis para a síntese de sistemas heterocíclicos nitrogenados.In this paper we report the use of microwaves as heat source to promote the synthesis of a series of nitroketene N,S-acetals with good to excellent isolated yields. These compounds are very useful intermediates for synthesizing nitrogen-containing heterocycles.

Chemistry of Ketene N,S-Acetals: An Overview

“…By use of microwaves (MW) as heat source, a series of nitroketene N , S -acetals bearing N -aryl and N -alkyl groups were prepared by reaction of 27 with the corresponding amines (Scheme ). In comparison, no reaction occurred when 4-nitroaniline and 4-(trifluoromethyl)­aniline were applied, respectively, due to their weak nucleophility resulting from the strong EWG (nitro and trifluoromethyl group) on the aryl ring of the arylamine. , …”

“…In comparison, no reaction occurred when 4nitroaniline and 4-(trifluoromethyl)aniline were applied, respectively, due to their weak nucleophility resulting from the strong EWG (nitro and trifluoromethyl group) on the aryl ring of the arylamine. 84,85 Trifluoroacetyl is a strong EWG. 86,87 Displacement of a methylthio group of trifluoroacetyl ketene dimethylthioacetal 88,89 by an amine gives the desired trifluoroacetyl ketene N,Sacetals, for example 30a−f, in good to excellent yields under very mild reaction conditions (Scheme 9) 90 without requirement for an external base.…”

NitroketeneN,S-acetals: synergistic building blocks for the synthesis of heterocycles

“…The same starting component 15 was explored by Sangi and Correa to generate a short library of nitroketene N,S-acetals 21 via the reaction of 15 with one equivalent of a number of primary amines 20 under microwave irradiation with high yields (Scheme 6). 35 Again, similar conditions were utilized for the synthesis of the cyclic and acyclic nitroketene N,S-acetals 23 and 25 by the same group (Scheme 7). 36 Dunkern et al described a slightly modied protocol for the synthesis of the nitroketene N,S-acetal derivatives 28 from 15, as depicted in Scheme 8.…”

Microwave-Assisted Synthesis of Nitroketene N,Oaminoacetals and Nitroketene N,N-aminals

“…They can further be converted into the corresponding S,N-and N,N-ketals, 2 and 3 respectively, making them important as precursors for a large variety of functionalized ketals. 2 As part of our studies on ketene dithioacetal for the synthesis of heterocyclics, we found that microwave irradiation accelerates the vinylic substitution of the anilines and amines in nitroketene S,S-acetals 3 . In this work, we report the annulation reaction of hydroxylamines and diamines to the formation of the heterocyclic compounds.…”