Correction. Alkyl-Substitution Effects in the Photochemistry of 2-Cyclohexenones

Abstract

Pages 73-79. The reaction of cyclopropylphenylcarbinol with phosphorus tribromide at -15°g ives 4rbromo-l-phenyl-1-butene, identified by its nmr spectrum and by its conversion to trans-1phenyl-1,3-butadiene on treatment with sodium amide in liquid ammonia, rather than cyclopropylphenylcarbinyl bromide, in confirmation of the report of A. Maercker and J. D. Roberts, J.

Spiroketones and a Biphenyl Analog from Stems and Leaves of Larrea nitida and Their Inhibitory Activity against IL-6 Production

“…The exciton splitting theory supported its R configuration. From the UV and CD spectrum, the negative exciton-split Cotton effect at 220 nm was observed due to the π→π * intramolecular charge-transfer transition of a 4-methoxyphenyl chromophore and a 2-cyclohexenone chromophore [ 18 , 19 ]. The negative exciton-split Cotton effect indicated that the two electric transition moments of these chromophores were rotated in a counterclockwise direction, as shown in Figure 2 c.…”

Research Note

“…Trans-cyclohexenones have been suggested as intermediates in photoannelation reactions of 4,4-dimethyl cyclohexenone (DMCH) based upon flash kinetic data (Schuster et al, 1987), and have recently been implicated by Rudolph and Weedon (1989) in the acidcatalyzed photoaddition of methanol to, and photochemical deconjugation of, 3-alkyl-2-cyclohexenones. However, the observation that 1 -(0, + 0,) = 0.02 2 0.02 for DMCH and the parent system leaves much too small a fraction of the original excitation available to account for formation of trans-fused photocycloadducts with a quantum yield as high as 0.5 (Schuster et al, 1987) via ground state trans-cyclohexenones of measurable lifetime at room temperature; the small heat discrepancy for the 3-alkyl enones could be due to the formation of low yields of deconjugated isomers (Dauben et a/., 1968;Rudolph and Weedon, 1989). However, such trans-cyclohexenones would not be detected in these PAC experiments if their lifetimes were of the order of the enone triplet, i.e.…”