DNMR, DFT and preparative study on the conformation of (Z)-4,5,6,7-tetrahydropyrazolo[1,5-e]benzo[g][1,5]diazonin-8-ones and (Z)-4,5-dihydropyrazolo[1,5-d]benzo[f][1,4]diazocin-7(6H)-ones

Ádám Gyömöre, Zoltán Kovács, Tibor Nagy, Veronika Kudar, András Szabó, A. Csámpai

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

By means of base-catalyzed ring enlargement of triazaindenoindenes and pentalenoindenes obtained from anhydride-induced ring transformation of 3,4-dihydro-2H-pyrimido- and 2,3-dihydroimidazo[2,1-a]phthalazinium-olates, respectively, a series of pyrazolo[1,5-e]benzo[g][1,5]diazonin-8-ones and pyrazolo[1,5-d]benzo[f][1,4]diazocin-7(6H)-ones were obtained. Alternative pathways and energetics for the ring inversion of symmetrically substituted medium-size ring systems were determined by combined use of DNMR measurements and B3LYP/6-31G(d,p) calculations using the IEFPCM solvent model. One pyrazolobenzodiazonine carrying hydrogen at the C1 position was found to undergo facile ring inversion by a two-step mechanism, while 1-Me and 1-Ph substituents rendered complete rigidity to this ring system. A three-step mechanism was revealed for the ring inversion of the two studied pyrazolobenzodiazocines with energetics practically invariant to the investigated C1-substituents (H and Me). The attempted RCM of the N,O-diallyl derivative of a selected rigid model effected by Grubbs II catalyst led to deallylation and olefin isomerization avoiding the formation of bridged products with enhanced skeletal strain. A tolerable degree of ring strain associated with negligible skeletal distortion could be introduced into the same benzodiazonine by N,O-dialkylation with 1,3-bis(bromomethyl)benzene.

Original languageEnglish
Pages (from-to)10837-10848
Number of pages12
JournalTetrahedron
Volume64
Issue number48
DOIs
Publication statusPublished - Nov 24 2008

Fingerprint

Anhydrides
Alkenes
Benzene
Discrete Fourier transforms
Conformations
Hydrogen
Isomerization
Rigidity
Derivatives
Catalysts

Keywords

  • Benzodiazocine
  • Benzodiazonine
  • Conformational flexibility
  • DFT
  • DNMR
  • Ring inversion

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry
  • Drug Discovery

Cite this

DNMR, DFT and preparative study on the conformation of (Z)-4,5,6,7-tetrahydropyrazolo[1,5-e]benzo[g][1,5]diazonin-8-ones and (Z)-4,5-dihydropyrazolo[1,5-d]benzo[f][1,4]diazocin-7(6H)-ones. / Gyömöre, Ádám; Kovács, Zoltán; Nagy, Tibor; Kudar, Veronika; Szabó, András; Csámpai, A.

In: Tetrahedron, Vol. 64, No. 48, 24.11.2008, p. 10837-10848.

Research output: Contribution to journalArticle

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AU - Gyömöre, Ádám

AU - Kovács, Zoltán

AU - Nagy, Tibor

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