A Switchable Protocol for Selective Synthesis of gem‐Dibromo Compounds and Amides from Ketoximes using TsNBr₂

Abstract

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.

Unanticipated switch of reactivity of isonitrile via N≡C bond scission: Cascade formation of symmetrical sulfonyl guanidine

“…N,N -Dibromoarylsulfonamides are an important class of organic reagents used in various organic transformations. 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 In continuation of our effort in the development of synthetic methods with such reagents, herein, we disclose a new pathway for complete cleavage of C-N triple bond of isonitrile which leads to the formation of symmetrical guanidines. Interesting feature of this reaction is that in the initial phase, isonitrile works as a source of carbodiimide reacting via C-end of the isonitrile where no cleavage of C≡N bond occurs.…”