Enolization of Delta9,10-Octal-1-one: relative stabilities of s-trans exocyclic and s-cis endocyclic dienolates.
Delta9,10-Octal-1-one (3,4,5,6,7,8-hexahydro-1(2H)-naphthalenone, 1) can be deprotonated at either of its two gamma positions to form the isomeric exocyclic (1-exo) and endocyclic (1-endo) dienolates. The rate of deuterium exchange for the gammaexo protons of 1 (1.6(+/-0.1)x10(-4) M-1 s-1) is 12-fold faster than that for those at the gammaendo position (1.38(+/-0.08)x10(-5) M-1 s-1). Assuming a Brønsted coefficient of 0.5, these results indicate that the exocyclic dienolate is 3.0 kcal/mol more stable than its endocyclic counterpart.
Hawkinson
David C
DC
Department of Chemistry, University of South Dakota, Vermillion, South Dakota 57069, USA. david.hawkinson@usd.edu
Wang
Ying
Y
D002625:Chemistry, Organic / Q000379:methods*; D006844:Hydrocarbons, Cyclic / Q000737:chemistry*; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry*
C520780:(3,4,5,6,7,8-hexahydro-1(2H)-naphthalenone); D006844:Hydrocarbons, Cyclic; D009281:Naphthalenes