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Org Biomol Chem. 2011 Sep 7;9(17):6040-54. doi: 10.1039/c1ob05460k. Epub 2011 Jul 13.

Sigmatropic rearrangements in 5-allyloxytetrazoles.

Author information

1
Department of Chemistry and Pharmacy, F.C.T. and CCMAR, University of Algarve, Campus de Gambelas, 8005-039 Faro, Portugal.

Abstract

Mechanisms of thermal isomerization of allyl tetrazolyl ethers derived from the carbocyclic allylic alcohols cyclohex-2-enol and 3-methylcyclohex-2-enol and from the natural terpene alcohol nerol were investigated. In the process of the syntheses of the three 1-aryl-5-allyloxytetrazoles, their rapid isomerization to the corresponding 1-aryl-4-allyltetrazol-5-ones occurred. The experiments showed that the imidates rearrange exclusively through a [3,3']-sigmatropic migration of the allylic system from O to N, with inversion. Mechanistic proposals are based on product analysis and extensive quantum chemical calculations at the DFT(B3LYP) and MP2 levels, on O-allyl and N-allyl isomers and on putative transition state structures for [1,3']- and [3,3']-sigmatropic migrations. The experimental observations could be only explained on the basis of the MP2/6-31G(d,p) calculations that favoured the [3,3']-sigmatropic migrations, yielding lower energies both for the transition states and for the final isomerization products.

PMID:
21750817
DOI:
10.1039/c1ob05460k
[Indexed for MEDLINE]

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