The mechanism of the photochemical rearrangement of lumisantonin

Abstract

For PhzCO + hv + In conversions in excess of 50%, the reaction mixture at the end of the dark reaction will contain In, which will ultimately have to react with atmospheric oxygen upon admission of air. one can easily obtain quantum Yields of Ph2CO disappearance ranging from 1 to 2. The only case in which this quantum yield can be close to 2 is if the Abstract: Sensitization studies on the photolysis of lumisantonin together with a reinvestigation of its pyrolysis have yielded results which support a mechanism involving five discreet steps: (1) excitation; (2) intersystem crossing; (3) bond breaking; (4) electron demotion and relaxation to a dipolar state; (5) rearrangement. Photolysis at low temperature in a matrix allowed the trapping of a colored intermediate the lifetime and spectral characteristics of which are consistent with the postulated dipolar state. The possibilities of electron ejection from an excited state or reaction uia vibrationally excited ground states are discussed and considered to be unlikely in this system. or several years interest has centered on "ionic"

Substituent and solvent influence on the nature of the oxyallyl intermediate in the rearrangement of bicyclo[3.1.0]hex-3-en-2-ones

“…It has been suggested that oxyallyl compounds are intermediates in both thermal and photochemical rearrangements of bicyclo[3.1.0]hex-3-en-2-ones to phenols [25][26][27][28][29][30][31][32][33][34][35]. Some time ago, we studied the reaction pathway for the prototype rearrangement of bicyclo[3.1.0] hex-3-en-2-one (1a) to phenol (3a) in the gas phase at the CASSCF/CASPT2 level [36].…”

Mechanism of the photoconversion of 5, 5-dimethylbicyclo- [4.1.0] hept-3-en-2-one to 2,3,5-trimethylphenol and 3,4,5-trimethylphenol

“…The substituent effect of a methyl group at C-2 and C-4 was also studied in the octalone system (16,17). Dienone 38 which has a C-2 methyl gave a bicyclic enone (39)…”

Photochemical studies of some 2-cyclohexenones

“…The spectroscopic investigation of six steroidal ketones (5)(6)(7)(8)(9)(10) by phosphorescence excitation and emission methods was carried out by Keams and coworkers in 1968 (3, 4). Direct absorption and phosphorescence excitation 3 * techniques allowed location of the (n,TT ) states.…”

“…Fisch and Richards(8) have investigated the triplet state of lumissntonin (3^) by phosphorescence techniques. The molecule exhibits a weak structureless emission with the 0-0 band at 64-+ kcal/mole.…”