title: 1,3-dipolar cycloaddition of 2-dialkylaminothioisomünchnones with aliphatic aldehydes: synthesis of beta-lactams and thiiranes, structure elucidation, and rationale for chemoselective fragmentation of cycloadducts.
abstract: A series of highly funtionalized beta-lactams and thiiranes can be generated on treatment of 1,3-thiazolium-4-olates (thioisomünchnones) with aliphatic aldehydes. Although in some cases a variety of products have been obtained, the present paper now provides a mechanistic rationale to explain the product distribution based on stereoelectronic effects. Thus, ring fragmentation of the initial [3+2] cycloadduct is essentially dictated by the electronic character of the aryl substituent on the nitrogen atom of the parent thioisomünchnone. However, further evolution of such cycloadducts into beta-lactams or thiiranes is governed by steric effects to a large extent. Evidence for such interactions has been obtained by computing PM3-optimized diastereomeric transition structures in the reaction of a thioisomünchnone with a chiral aliphatic aldehyde.
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Extremadura, E-06071 Badajoz, Spain.
authors.forename: Martin
authors.initials: M
authors.lastname: Avalos
authors.forename: Reyes
authors.initials: R
authors.lastname: Babiano
authors.forename: Pedro
authors.initials: P
authors.lastname: Cintas
authors.forename: Fernando R
authors.initials: FR
authors.lastname: Clemente
authors.forename: Ruth
authors.initials: R
authors.lastname: Gordillo
authors.forename: José L
authors.initials: JL
authors.lastname: Jiménez
authors.forename: Juan C
authors.initials: JC
authors.lastname: Palacios