Saito F, Becker J, Schreiner PR. Synthesis and Conformational Analysis of Parent Perhydroazulenes Reveal an Energetically Preferred cis Ring Fusion.
J Org Chem 2020;
85:4441-4447. [PMID:
32073267 DOI:
10.1021/acs.joc.0c00167]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Perhydroazulenes are common structural motifs in various terpene natural products. Herein, we present the synthesis of parent cis- and trans-perhydroazulenes. Conformational analysis performed with density functional theory (DFT, e.g., B3LYP, M06-2X) and MP2 geometry optimizations with a cc-pVTZ basis set, followed by CCSD(T)/cc-pVTZ single-point energy computations reveals that the cis isomer is 0.7 kcal mol-1 more stable than the trans isomer. Steric and torsional strains present in the trans isomer are responsible for this unexpected relative cis/trans stability.
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