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Ghavtadze N, Fröhlich R, Würthwein EU. Acid-mediated electrocyclic domino transformations of 5,5-disubstituted 1-amino-1-azapenta-1,4-dien-3-ones into dihydrospiroindenepyrazole and dihydroindenodiazepine derivatives. J Org Chem. 2009;74(12):4584-91doi: 10.1021/jo900270e.
Ghavtadze, N., Fröhlich, R., & Würthwein, E. U. (2009). Acid-mediated electrocyclic domino transformations of 5,5-disubstituted 1-amino-1-azapenta-1,4-dien-3-ones into dihydrospiroindenepyrazole and dihydroindenodiazepine derivatives. The Journal of organic chemistry, 74(12), 4584-91. https://doi.org/10.1021/jo900270e
Ghavtadze, Nugzar, et al. "Acid-mediated electrocyclic domino transformations of 5,5-disubstituted 1-amino-1-azapenta-1,4-dien-3-ones into dihydrospiroindenepyrazole and dihydroindenodiazepine derivatives." The Journal of organic chemistry vol. 74,12 (2009): 4584-91. doi: https://doi.org/10.1021/jo900270e
Ghavtadze N, Fröhlich R, Würthwein EU. Acid-mediated electrocyclic domino transformations of 5,5-disubstituted 1-amino-1-azapenta-1,4-dien-3-ones into dihydrospiroindenepyrazole and dihydroindenodiazepine derivatives. J Org Chem. 2009 Jun 19;74(12):4584-91. doi: 10.1021/jo900270e. PMID: 19459598.
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J Org Chem. 2009 Jun 19;74(12):4584-91. doi: 10.1021/jo900270e.

Acid-mediated electrocyclic domino transformations of 5,5-disubstituted 1-amino-1-azapenta-1,4-dien-3-ones into dihydrospiroindenepyrazole and dihydroindenodiazepine derivatives.

The Journal of organic chemistry

Nugzar Ghavtadze, Roland Fröhlich, Ernst-Ulrich Würthwein

Affiliations

  1. Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Münster, Germany.

PMID: 19459598 DOI: 10.1021/jo900270e

Abstract

Trifluoromethyl-substituted 1-amino-1-azapenta-1,4-dien-3-ones 4, which are accessible in good yield from pyruvates 1 in a three-step procedure, undergo a cascade reaction involving inter alia two electrocyclizations upon treatment with a large excess of trifluoromethanesulfonic acid to give novel dihydrospiroindenepyrazole 5a-o and dihydroindenodiazepine 6a-j. We interpret this sequence of reactions on the basis of quantum chemical calculations as a dicationic cyclization of a pentadien-1-one ("superelectrophilic solvation"), where one of the double bonds is part of an aromatic ring and a subsequent rearrangement to form an (monocationic) iminium ion, which either cyclizes to give five-membered spiro ring systems (compounds 5) or tricyclic dihydroindenodiazepine derivatives 6. Huckel- and Mobius-type transition states of the electrocyclization reactions are discussed considering the results of NICS calculations. One 1-amino-1-penta-1,4-dien-3-one 4 and several dihydrospiroindenepyrazoles 5 and dihydroindenodiazepines 6 could be characterized by X-ray diffraction.

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