title: Diels-Alder reactions of 4-alkenylthiazoles: a new approach to thiazole functionalization.
abstract: Somewhat unexpectedly, the computed highest occupied molecular orbital (HOMO) energies of some 4-alkenylthiazoles afforded values close to those calculated for the Danishefsky-Kitahara and Rawal dienes. In fact, 4-alkenylthiazoles behave as all-carbon dienes in Diels-Alder reactions with the participation of the formal C-C double bond of the thiazole ring and the side-chain double bond. The reactions with N-substituted maleimides, maleic anhydride, and naphthoquinone take place with high levels of stereocontrol to give the corresponding endo-cycloadducts in good to excellent yields. Depending on the dienophile, the cycloadduct further transforms under the reaction conditions through either a 1,3-hydrogen shift, dehydrogenation, or an ene reaction or Michael addition with another molecule of dienophile. These unprecedented results open new synthetic perspectives for the functionalization of the thiazole ring.
authors.affiliation: Departamento de Química Orgánica, Facultad de Química, and Servicio de Instrumentación Científica, Universidad de Murcia, Campus de Espinardo, 30100 Murcia, Spain. alajarin@um.es
authors.forename: Mateo
authors.initials: M
authors.lastname: Alajarín
authors.forename: José
authors.initials: J
authors.lastname: Cabrera
authors.forename: Aurelia
authors.initials: A
authors.lastname: Pastor
authors.forename: Pilar
authors.initials: P
authors.lastname: Sánchez-Andrada
authors.forename: Delia
authors.initials: D
authors.lastname: Bautista
mesh_terms: D000466:Alkadienes; D008299:Maleic Anhydrides / Q000737:chemistry; D008301:Maleimides / Q000737:chemistry; D008958:Models, Molecular; D009285:Naphthoquinones / Q000737:chemistry; D013844:Thiazoles / Q000737:chemistry*
chemical_list: D000466:Alkadienes; D008299:Maleic Anhydrides; D008301:Maleimides; D009285:Naphthoquinones; D013844:Thiazoles