Sigmatropic Shifts in Allene Oxide Rearrangements: First General Route to [3,4] Shifts in Aliphatic Systems

Abstract

COMMUNICATIONS 390 nm is absent in the crystals, the intramolecular hydrogen bond of the dye within the complex is not perturbed by the cyclic oligosaccharide host.The dye-trapping process in aqueous solution can also be monitored by the biphasic behavior of the fluorescence intensity at 390 nm as a function of p-CD concentration. Thus, at low concentrations of p-CD the intensity of this band initially increases ( Figure 2B) due to protection of the emitting fluorophore by p-CD. This trend is reversed and the intensity starts to decline upon further increase of the oligosaccharide concentration, with the simultaneous appearance of the band at 550 nm, as noted above. The BH analysis of the initial change of the intensity at 390 nm yields a 1 : 1 stoichiometry and a binding constant K , = 500 M-' The equilibrium constant K2 of the 1 :2

Rearrangements of organic peroxides and related processes

“…The replacement of the vinyl group at the exocyclic double bond in the fulvene precursor by a 3-butenyl group and the thermal decomposition of the resulting endoperoxides 535 at 80 °C lead to a [3,4]-sigmatropic shift of the 3-butenyl group and formation of the 5-oxo-6-heptenal derivatives 536 . The mechanism of this process involves the formation of epoxide A , which undergoes a [3,4]-shift through the intermediate B [ 494 ] ( Table 27 ).…”

1,2-Dihydropentalenes from Fulvenes by [6 + 2] Cycloadditions with 1-Isopropenylpyrrolidine

“…4 Inspired by Hafner’s intramolecular enamine cyclization method, Houket al reported formal intramolecular [6 + 2] enamine–fulvene cycloadditions to give linearly fused tricyclic 1,2-dihydropentalenes in low to moderate yields. 5,6 In our continued effort to extend the photooxygenation chemistry of fulvenes 7 to bicyclic analogues, we required a convenient synthesis of the only dihydropentalene isomers, 1,2-dihydropentalenes, that contain the fulvene moiety. Herein we report a general and versatile synthesis of 1,2-dihydropentalenes based on intermolecular fulvene–enamine [6 + 2] cycloadditions.…”

Computational Treatments of Peroxy Radicals in Combustion and Atmospheric Reactions

“…Selected italicized hydrogen bond lengths in angstrom are from previously unpublished 158 B3LYP/6-311G(d,p) geometry optimizations be classified as a 3,4-sigmatropic shift. This particular kind of rearrangement 162 is not commonly observed, but there is experimental evidence for this process in allene oxides via a zwitterionic oxyallyl intermediate 163 and in the reaction of allylic alcohols with Fischer carbene complexes 162 . The acetic acid-ozone complex (20) then dissociates to give the final products.…”