Fused munchnones in recyclization tandems

This result can be clearly explained in terms of higher electron deficiency of the isoquinolinium than that of the pyridinium ring. The presence of a leaving group at a-posi- tion of the initial pyridinium salt would favor cyclization. We found that 2-chloropyridinium salts IVa,b in reaction with carbon disulfide at room temperature form the desired mesoionic thiazolopyridines Va,b (5). Structure of the com- pound Va was confirmed by X-ray analysis.