Aza-Diels-Alder versus 1,3-Dipolar Cycloadditions of Methyl Glyoxylate Oxime with Cyclopentadiene

The 12th International Electronic Conference on Synthetic Organic Chemistry session Computational ChemistryThe acid-catalyzed [3+2] and [4+2] cycloadditions between methyl glyoxylate oxime (1) and cyclopentadiene were investigated using various Lewis and/or Bronsted acids at different temperatures in dichloromethane as solvent. Besides the expected new adducts, (±)-methyl [(3-exo)-2-hydroxy-2-azabicyclo[2.2.1]hept-5-ene]-3-carboxylate (2) and (±)-methyl [(3-endo)-2-hydroxy-2-azabicyclo[2.2.1]hept-5-ene]-3-carboxylate (3) a third addict, (±) methyl (1R,4R,5R)-(2-ox-3-azabicyclo[3.3.0]oct-7-ene)-4-carboxylate (4), whose formation can be explained by a concerted 1,3-dipolar cycloaddition, was obtained. Yields and product ratios were found to be more dependent on the catalyst than on the temperature; these results and the stereochemistry of the adducts, confirmed by spectroscopic data (1H and 13C NMR) and by X-ray cycloadditionsThis work was supported by Centro de Investigação em Química of University of Porto. The authors thank the Fundação para a Ciência e Tecnologia (FCT) for financial support of this work under project POCTI/QUI/44471/2002 (Pluri-annual and Programmatic Funding) and for the grant to C. A. D. Sousa (SFRH/BD/31526/2006