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Barriers to the intramolecular N- to N-transfer of different groups in pyrazoles: Prototropy vs. Elementotropy

✍ Scribed by Ibon Alkorta; José Elguero

Publisher: John Wiley and Sons
Year: 2005
Tongue: English
Weight: 184 KB
Volume: 16
Category: Article
ISSN: 1042-7163
DOI: 10.1002/hc.20163

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✦ Synopsis

Abstract

Barriers to the N‐ to N‐ transfer of different groups in pyrazole have been calculated at different levels (B3LYP and MP2 with 6‐31G*, 6‐311G*, and CEP‐121 basis sets). Ten groups studied were H, BH~2~, CH~3~, CHO, AlH~2~, SiH~3~, GaH~2~, GeH~3~, SnH~3~, and HgH. Two types of different transition states were found: The most common is a triangular situation with the group symmetrically linked to both N atoms. For metals M of the group 13 (B, Ga, Al) that situation is a second minimum while the TS corresponds to a rotation about the NM bond plus a displacement of the migrating group to yield a nonsymmetric TS. A relationship between the barrier and the geometry has been found. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:628–636, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20163

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