An efficient one pot strategy has been developed for the synthesis of 2-acylbenzothiazoles and quinoxalines from aryl methyl ketones. A variety of heterocycles of these two categories could be prepared in a two-step sequence in excellent yields. The reaction was performed starting from aromatic ketones via an aryl gloxal intermediate which, on further condensation with 2-aminobenzenethiol or o-phenylenediamine, produces the corresponding heterocyclic skeleton. Aromatic ketones are initially treated with TsNBr 2 in DMSO at 65°C for 3 h and the crude reaction mixture was treated with 2-aminobenzenethiol (at 80°C) or o-phenylenediamine (at RT) to generate the final compound.
A new synthetic procedure has been developed for the synthesis of primary aromatic amide from different types of styrene and phenylacetylene using TsNBr 2 , I 2 -aqueous NH 3 solution at room temperature. The reaction proceeds via the formation of α-bromoketone & α,α-dibromoketone as intermediate from styrene and phenylacetylene respectively in the presence of TsNBr 2 at the initial stage of the reaction. Subsequent treatement of the reaction mixturewith molecular iodine and aq. NH 3 (25%) produces the corresponding amide. Various primary aromatic amides were obtained in appriciable yield at room temperature.
A base controlled metal‐free method for selective synthesis of N‐substituted amide and α,α–dibromoketones have been developed by treating ketoximes with N,N‐dibromo‐p‐toluenesulfonamide (TsNBr2) within a very short reaction time. Interesting feature of the process is that the product selectivity can be switched just by addition or exclusion of the base under the identical reaction condition. It was found that addition of a base in the reaction mixture drives the reaction towards a pathway which is completely different from that without having the additive in the medium. Additionally, another novel strategy has also been developed for synthesis of 1‐(dibromomethyl)benzenes directly from aldehyde using TsNHNH2 and TsNBr2 under metal‐free condition.
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