Triethylamine-promoted cycloaddition reactions of N-phenacyl and N-alkoxycarbonylmethylbenzothiazolium bromides with aromatic aldehydes and malononitrile (ethyl cyanoacetate, pivaloylacetonitrile) in ethanol afforded functionalized tetrahydrobenzo[d]pyrrolo[2,1-b]thiazoles in good yields and various diastereoselectivity. The oxidation reaction… Click to show full abstract
Triethylamine-promoted cycloaddition reactions of N-phenacyl and N-alkoxycarbonylmethylbenzothiazolium bromides with aromatic aldehydes and malononitrile (ethyl cyanoacetate, pivaloylacetonitrile) in ethanol afforded functionalized tetrahydrobenzo[d]pyrrolo[2,1-b]thiazoles in good yields and various diastereoselectivity. The oxidation reaction of the functionalized tetrahydrobenzo[d]pyrrolo[2,1-b]thiazoles with DDQ in different solvents resulted in diverse benzothiazole derivatives and benzo[d]pyrrolo[2,1-b]thiazoles. The reaction mechanism and the stereochemistry of this tandem [3 $$+$$+ 2] cycloaddition reaction and sequential oxidation reaction are illustrated based on analysis of the reactive intermediates and obtained products.Graphical Abstract
               
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