| Abstract
| - A series of highly funtionalized β-lactams and thiiranes can be generated on treatment of 1,3-thiazolium-4-olates (thioisomünchnones) with aliphatic aldehydes. Although in some cases a varietyof products have been obtained, the present paper now provides a mechanistic rationale to explainthe 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 thenitrogen atom of the parent thioisomünchnone. However, further evolution of such cycloadductsinto β-lactams or thiiranes is governed by steric effects to a large extent. Evidence for suchinteractions has been obtained by computing PM3-optimized diastereomeric transition structuresin the reaction of a thioisomünchnone with a chiral aliphatic aldehyde.
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