John L. Thompson

Hammett analysis of a family of carbene-carbene complex equilibria.

p-X-substituted phenylchlorocarbenes (X = NO(2), CF(3), Cl, H, Me, and MeO) form π-type complexes with trimethoxybenzene in pentane. The carbenes and complexes are in equilibrium, and logarithms of the measured equilibrium constants are well correlated by Hammett σ(p) constants with ρ = 2.48. The carbene complexes are characterized by UV-vis spectroscopy, and computational analysis is afforded by DFT calculations.

Evolution of Structure and Reactivity in a Series of Iconic Carbenes

We present experimental activation parameters for the reactions of six carbenes (CCl(2), CClF, CF(2), ClCOMe, FCOMe, and (MeO)(2)C) with six alkenes (tetramethylethylene, cyclohexene, 1-hexene, methyl acrylate, acrylonitrile, and α-chloroacrylonitrile). Activation energies range from -1 kcal/mol for the addition of CCl(2) to tetramethylethylene to 11 kcal/mol for the addition of FCOMe to acrylonitrile. A generally satisfactory analysis of major trends in the evolution of carbenic structure and reactivity is afforded by qualitative applications of frontier molecular orbital theory, although the observed entropies of activation appear to fall in a counterintuitive pattern. An analysis of computed cyclopropanation transition state parameters reveals significant nucleophilic selectivity of (MeO)(2)C toward α-chloroacrylonitrile.

A total synthesis of (±)-prostaglandin E3 methyl ester via endo-bicyclohexane intermediates

(±)-Prostaglandin E3 methyl ester has been synthesized via endo-bicyclohexane intermediates.