title: Synthesis of chiral pyrrolo[1,2-c]thiazoles via intramolecular dipolar cycloaddition of münchnones: an interesting rearrangement to pyrrolo[1,2-c]thiazines.
abstract: Intramolecular dipolar cycloaddition of bicyclic münchnones, 5H,7H-thiazolo[3,4-c]oxazol-4-ium-1-olates, derived from cyclodehydration of 2-substituted-N-acylthiazolidine-4-carboxylic acids are reported. A range of new pyrrolo[1,2-c]thiazole derivatives (7, 14, 15, 20, 23, and 26) were obtained as single enantiomers from 2-phenylthiazolidines, 2-benzoylthiazolidines, and 2-methylthiazolidine-4-carboxylates. Pyrrolo[1,2-c][1,4]thiazine derivative 27 was also obtained from pyrrolo[1,2-c]thiazole derivative 26. The structures of methyl (2R,4R)-2-(p-methoxybenzoyl)thiazolidine-4-carboxylate (17a), methyl (2R,4R)-2-(p-methoxybenzoyl)-N-(prop-2-ynyloxyacetyl)thiazolidine- 4-carboxylate (18), and 3-oxo-4-phenyl-3,4,6,8-tetrahydro-1H-furo[3',4':2,3]pyrrolo[1,2-c][1,4]thiazine (27) were determined by X-ray crystallography. Chirooptical studies of the pyrrolo[1,2-c]thiazoles were done by confirming the absolute configuration at the chiral center C-3.
authors.affiliation: Departamento de Química, Universidade de Coimbra, 3004-535, Portugal. tmelo@ci.uc.pt
authors.forename: Teresa M V D
authors.initials: TM
authors.lastname: Pinho e Melo
authors.forename: Maria I L
authors.initials: MI
authors.lastname: Soares
authors.forename: António M d'A
authors.initials: AM
authors.lastname: Rocha Gonsalves
authors.forename: José A
authors.initials: JA
authors.lastname: Paixão
authors.forename: Ana M
authors.initials: AM
authors.lastname: Beja
authors.forename: Manuela Ramos
authors.initials: MR
authors.lastname: Silva
authors.forename: Luiz
authors.initials: L
authors.lastname: Alte da Veiga
authors.forename: João Costa
authors.initials: JC
authors.lastname: Pessoa