Base‐Mediated Synthesis of 1,3‐Diazaphenothiazines from 2‐Methylbenzothiazoliums, Aryl Aldehydes and Amidines

Abstract

In this study, we developed a process for the [2+1+3] cyclisation of 2‐methylbenzothiazole salts, aldehydes, and amidine hydrochlorides to synthesise 1,3‐diazaphenothiazines under mild conditions. This metal‐free reaction is performed in ethanol and uses oxygen as an oxidant. Various 2‐methylbenzothiazole salts, aldehydes, and amidine hydrochlorides were well tolerated, providing the target products with acceptable yields.

One-Pot Tandem/Spirocyclization Reaction: Synthesis of Spiro[pyridine-thiazolidine] Ring Derivatives

“…Therefore, although constructing structurally novel spirothiazole spirocyclic backbone molecules using environmentally friendly methods is challenging, it holds considerable research value. Recently, our group successfully developed a [2 + 1 + 3] cyclization ring-opening recombination strategy of 2-methylbenzothiazolium salts, aldehydes, and amidinones for the synthesis of 1,3-diazaphenothiazines (Scheme b) . As a part of our ongoing project, we considered the feasibility of extending this strategy to the construction of spiro[pyridine-thiazolidine]-ring derivatives.…”