Synthesis and structural studies of some [1(4)]paracyclo-bis-(1,2)pyrazolium- and (1,3)imidazolium-phanes

Authors
Cabildo, P Sanz, D Claramunt, RM Bourne, SA Alkorta, I Elguero, J
Citation
P. Cabildo et al., Synthesis and structural studies of some [1(4)]paracyclo-bis-(1,2)pyrazolium- and (1,3)imidazolium-phanes, TETRAHEDRON, 55(8), 1999, pp. 2327-2340
Citations number
34
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
TETRAHEDRON
ISSN journal
00404020 → ACNP
Volume
55
Issue
8
Year of publication
1999
Pages
2327 - 2340
Database
ISI
SICI code
0040-4020(19990219)55:8<2327:SASSOS>2.0.ZU;2-9
Abstract
The crystal and molecular structure of [1(4)]paracyclo-bis-(1,2)pyrazoliump hane dibromide (la) has been determined. The compound exists in the solid s tate in the chair (C) conformation while both chair (C) and boat (B) confor mations are present in solution in comparable amounts. The barrier to the C reversible arrow B interconversion has been determined by H-1 NMR spectros copy (Delta G(double dagger) approximate to 17 kcal mol(-1)). AM1 semiempir ical calculations conveniently reproduce the difference ill stability betwe en the chair (C) and the boat (B) conformations. (C) 1999 Elsevier Science Ltd. All rights reserved.