Diastereoselective synthesis of spiro[benzo[d]pyrrolo[2,1-b]thiazole-3,3'-indolines] via cycloaddition reaction of N-phenacylbenzothiazolium bromides and 3-methyleneoxindoles.

The domino cycloaddition reactions of N-phenacylbenzothiazolium bromides with 3-phenacylideneoxindoles or ethyl 2-(2-oxoindolin-3-ylidene)acetates in ethanol at room temperature in the presence of triethylamine as a base afforded functionalized spiro[benzo[d]pyrrolo[2,1-b]thiazole-3,3'-indolines] in good yields and with high diastereoselectivity. The similar reactions of N-phenacylthiazolium bromides with 3-phenacylideneoxindoles resulted in the corresponding functionalized spiro[indoline-3,7'-pyrrolo[2,1-b]thiazoles] in satisfactory yields and also with high diastereoselectivity.