1,2-Didehydro[10]annulenes: structures, aromaticity, and cyclizations

Armando Navarro-Vázquez; Peter R Schreiner

doi:10.1021/ja0507968

1,2-Didehydro[10]annulenes: structures, aromaticity, and cyclizations

J Am Chem Soc. 2005 Jun 8;127(22):8150-9. doi: 10.1021/ja0507968.

Authors

Armando Navarro-Vázquez¹, Peter R Schreiner

Affiliation

¹ Institute of Organic Chemistry, Justus-Liebig-University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany.

PMID: 15926843
DOI: 10.1021/ja0507968

Abstract

The conformational space of C(10)H(8) 1,2-didehydro[10]annulenes, along with their unimolecular conversion to isonaphthalenes (cyclic allenes), has been studied computationally using DFT (B3LYP), single-reference [CCSD(T)], and multireference (MCQDPT2) post-HF methods. The introduction of the linear alkynyl moiety releases enough angle strain to make a nearly planar "heart" aromatic form the preferred conformer by more than 6 kcal/mol [CCSD(T)] over a localized C(2) "twist" structure, as opposed to the closely related C(10)H(10) [10]annulene system. Computations also show that electrocyclic ring-opening of isonaphthalenes to the heart C(10)H(8) annulene takes place through a low barrier of 15 kcal/mol, and this should be considered the working mechanism for the reported isomerizations during dehydro Diels-Alder reactions of phenylacetylenes.