Generation and characterization of carbonyl ylides from pyrazolinone spirooxiranes

Laser flash photolyses of 1-oxa-5,6-diazaspiro[2.4]hept-6-ene-4-ones I (Ar [triple bond] Ph, p-NO2Ph, p-CH3OPh; R1 [tripe bond] CH3, Ph; R2, R3 [triple bond] CH3; R2 [triple bond] Ph, p-NO2Ph, p-ClPh, 2-naphthyl; R3 [triple bond] H) and of the symmetrical oxirane II give rise to transients with absorption spectra in the visible region and lifetimes of the order of 0.3 - 10 [mu]s in benzene at room temperature. Sensitization experiments in some cases indicate that the intermediate may arise from a triplet as well as a singlet excited state. Transients from I are quenched by alcohols and 2,3-dimethyl-2-butene whereas that from II is not. Steady state photolyses of I in methanol give products consistent with the assignment of the structure of the transient as a carbonyl ylide incorporating the pyrazolinone ring.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31041/1/0000718.pd

Environmental effects in the ESR spectra of organic triplet states

The effect of varying the environment on the zero-field parameters of triplet states is discussed. Variations can occur within a sample, the narrowest distributions being found when the geometry of the triplet approximates that of the host

Photooxygenations of sydnones and azomethine imines

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