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

Introduction to organic chemistry. Charles H. De Puy and Kenneth L. Rinehart, Jr. Wiley, New York, 1967, 392 pp. $8.95

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38748/1/150061128_ftp.pd

Organic Chemestry

xxi;ill.;1163hal.;26c

Photogeneration and thermogeneration of carbonyl ylides: 1,3-dipolar cycloadditions of 2,3-diaryloxiranes to dipolarophiles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24554/1/0000834.pd

Structural resolution of the stereochemistry of a spirooxirane derived from an α‐arylidene heterocyclic carbonyl. The crystal and molecular structure of 2‐( p ‐chlorophenyl)‐5‐phenyl‐7‐methyl‐1‐oxa‐5,6‐diazaspiro[2.4]hept‐6‐en‐4‐one

The stereochemical assignment of molecular geometry for α‐arylidene carbonyl compounds and spirooxirane derived from them have continued to be a challenging problem for which the most satisfactory solution continues to be an x‐ray diffraction structure determination. In that regard, the title compound (a spirooxirane) has been found to crystallize in the monoclinic space group P2 1/c with cell dimensions of a = 5.989(1)Å, b = 27.625(4)Å, c = 9.374(2)Å, β = 99.06(1)°. The structure of the compound has been determined, with the refinement to R = 0.059. The previous, tentative assignment of structure has been confirmed substantiating our prediction that the oxidation of the enone system proceeds with rotation of the phenyl group on the β‐carbon away from the carbonyl group, minimizing adverse steric interactions and allowing orbitals of the carbonyl group to overlap with those of the carbanionic center during the closure of the oxirane ring. The agreement between predictions based on nmr data and the x‐ray diffraction determination will support a stronger reliance on the nmr data predictions in subsequent studies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96401/1/5570200314_ftp.pd