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Synlett 2000; 2000(7): 0955-0958
DOI: 10.1055/s-2000-6661
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Easy Synthesis of New 2-Oxo-2,3-dihydro-1H-pyrrolo[1,2-b]pyrazole Systems

Orazio A. Attanasi* , Lucia De Crescentini, Paolino Filippone, Fabio Mantellini
  • *Istituto di Chimica Organica, Università, Piazza della Repubblica 13, 61029 Urbino, Italy; Fax + 39-0722-2907; E-mail: attanasi@uniurb.it
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Publication Date:
31 December 2000 (online)

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1,2-Diaza-1,3-butadienes react with dialkyl 1,3-acetonedicarboxylate in the presence of potassium carbonate to give 2-hydroxy-2,3-dihydro-1H-1-aminopyrroles that in turn produce 1-aminopyrroles by dehydration in the presence of copper(II)trifluoromethansulfonate. The treatment of these compounds with sodium hydride leads to NH-substituted 2-oxo-2,3-dihydro-1H-pyrrolo[1,2-b]pyrazole. Under the same reaction conditions, NH-BOC protected 1-aminopyrroles, after acidic cleavage of the BOC protecting group, afford NH-unsubstituted 2-oxo-2,3-dihydro-1H-pyrrolo[1,2-b]pyrazole.

1,2-diaza-1,3-butadienes - Michael additions - cyclization - pyrrolo[1,2-b]pyrazoles