title: Stepwise cycloaddition reaction of N-phenacylbenzothiazolium bromides and nitroalkenes for tetrahydro-, dihydro- and benzo[d]pyrrolo[2,1-b]thiazoles.
abstract: The triethylamine promoted stepwise 1,3-dipolar cycloaddition reaction of N-phenacylbenzothiazolium bromides with nitroalkenes in ethanol resulted in a mixture of two isomeric tetrahydrobenzo[d]pyrrolo[2,1-b]thiazoles with cis/trans/cis- and all-trans-configurations. More importantly, the corresponding dihydrobenzo[d]pyrrolo[2,1-b]thiazoles can be selectively prepared in refluxing ethanol and the benzo[d]pyrrolo[2,1-b]thiazoles can be obtained in satisfactory yields by sequential dehydrogenation with DDQ as oxidizer. On the other hand, the similar cycloaddition reaction of N-phenacylbenzothiazolium bromides with 1-methy-1-nitroalkenes in refluxing ethanol afforded benzo[d]pyrrolo[2,1-b]thiazoles with splitting out of nitro group. The stereochemistry of the spiro compounds was clearly elucidated on the basis of NMR spectra and sixteen single crystal structures.
authors.affiliation: College of Chemistry &Chemical Engineering, Yangzhou University, Yangzhou 225002, China.
authors.forename: Gong
authors.initials: G
authors.lastname: Jin
authors.affiliation: College of Chemistry &Chemical Engineering, Yangzhou University, Yangzhou 225002, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Sun
authors.affiliation: College of Chemistry &Chemical Engineering, Yangzhou University, Yangzhou 225002, China.
authors.forename: Ren-Yin
authors.initials: RY
authors.lastname: Yang
authors.affiliation: College of Chemistry &Chemical Engineering, Yangzhou University, Yangzhou 225002, China.
authors.forename: Chao-Guo
authors.initials: CG
authors.lastname: Yan