Thermal isomerizations of 2-d-1-(E)-propenylcyclobutanes to 4-d-3-methylcyclohexenes

John E Baldwin; Jean-Marie Fedé

doi:10.1021/ja0586586

Thermal isomerizations of 2-d-1-(E)-propenylcyclobutanes to 4-d-3-methylcyclohexenes

J Am Chem Soc. 2006 May 3;128(17):5608-9. doi: 10.1021/ja0586586.

Authors

John E Baldwin¹, Jean-Marie Fedé

Affiliation

¹ Department of Chemistry, Syracuse University, Syracuse, New York 13244, USA. jbaldwin@syr.edu

PMID: 16637607
DOI: 10.1021/ja0586586

Abstract

Racemic trans-2-d-1-(E)-propenylcyclobutane at 276 degrees C in the gas phase fragments to give ethylenes and pentadienes, equilibrates with its cis isomer, and rearranges to mixtures of 4-d- and 6-d-3-methylcyclohexenes through [1,3] carbon shifts. The time-dependent distributions of deuterium-labeled isomers of propenylcyclobutanes and 3-methylcyclohexenes reveal a significant secondary deuterium kinetic isotope effect favoring C1-C4 over C1-C2 bond breaking (kH/kD = 1.16 +/- 0.02) and a 72:28 preference for structural isomerizations giving (si + ar) rather than (sr + ai) products through conformationally flexible short-lived diradical intermediates.