Epoxidation of Allylic Alcohols with Hydrogen Peroxide Catalyzed by [PMO12O40]3-[C5H5N+(CH2)15CH3]3

The 13C NMR spectra of a series of epoxides derived from endo- and exo-dicyclopentadiene and their partially hydrogenated compounds were determined to examine the substituent effects arising from the introduction of the oxirane ring in comparison with those found in other ring systems. The 13C signals of some epoxides were assigned by using lanthanide shift reagents. Characteristic substituent effects exerted by an oxirane ring were demonstrated. Marked steric γ-effects of −8—13 ppm were observed at the bridge carbon signal in the bicyclo[2.2.1]heptane skeleton. Differences were found in the substituent effects between endo- and exo-dicyclopentadiene epoxides, and have been discussed in relation to the molecular geometry.

Carbon-13 NMR spectra of some epoxides derived from dicyclopentadiene

The stereochemical aspects of the cis-bicyclo[4.3.0]nona-3,7-diene epoxidation reaction by monoperoxyphthalic acid were investigated. The 1 H and 13 C NMR spectra of the stereoisomeric diepoxides obtained in this reaction have been studied experimentally and theoretically at the CSGT-PCM/PBE1PBE/6-31G ## (II) level. The application of combined experimental and theoretical NMR studies has allowed assignments of diepoxides to the corresponding stereoisomers to be made. The established trends of the influence of the orientation of the epoxide ring and the conformation of the bicyclic skeleton could be useful for stereochemical investigations of related polycyclic epoxidic compounds.

Identification of the stereoisomers of tetrahydroindene diepoxide by the 1H and 13C NMR characteristics : A combined experimental and theoretical study

Transition metals in organic synthesis annual survey covering the year 1979

Diels-Alder reactions between cyclopentadiene (CP) and butadiene (BD) give a variety of dimers such as 4-vinyl-cyclohexene (VCH), 5-vinyl-2-norbornene (VNB), cis-3a, 4, 7, 7a-tetrahydroindene (THI) and dicyclopentadiene (DCP), and these dimers contain two double bonds of different reactivity.In the present investigation, the epoxidation of these dimers with hydrogen peroxide catalyzed by metal oxides such as SeO2, H2MoO4 and H2WO4 was carried out under various reaction conditions, and the results obtained were compared with those of epoxidation with organic peracids.The reaction of VCH (1) with hydrogen peroxide catalyzed by SeO2 at 40°C for 5hr [Eq. (1)] did not give an epoxide but diol (2) in a 40% yield. In the oxidation of VCH by H2MoO4 and H2WO4 catalysts, diol (2) was also obtained but in lesser yields than by SeO2 catalyst.The epoxidation of VNB (3) with hydrogen peroxide by SeO2 yielded 33% monoepoxide (4), but H2MoO4 and H2WO4 catalysts were less selective [Eq. (2)].When THI (5) was epoxidized with hydrogen peroxide by SeO2 catalyst, monoepoxide (6) and indene (7) were obtained in 27% and 8% yields, respectively [Eq. (3)], while in the epoxidation by H2MoO4 and H2WO4 catalysts only (6) resulted in yields from 10 to 15%.On the other hand, the epoxidation of THI with perbenzoic acid yielded monoepoxides (6) and (8) in a 4:5 molar ratio and diepoxide (9) [Eqs. (4) and (5)].It was found that the present catalytic epoxidation indicated a higher selectivity for the epoxidation of THI compared with that of epoxidation with perbenzoic acid.For the formation of indene (7), it seems reasonable to assume that dehydrogenation is generally observed in the oxidation of cyclic compounds using SeO2.The epoxidation of DCP (10) occurred readily without any side reactions except when a V2O5 catalyst was used to give monoepoxides (11) and (12) as shown in Eq. (6).Effects of various solvents were examined in the reactions with the SeO2 catalyst, and it was found that epoxidation proceeded rapidly in a protonic solvent having a lower polarity such as tert-butyl alcohol.An extremely high ratio of (11)/(12) as compared with that of epoxidation by organic peracid was observed with the catalysts used. It is assumed that such high regioselectivity may be attributable to a steric effect established between the bridge head proton of the norbornene ring in DCP and the epoxidizing agent.

https://www.jstage.jst.go.jp/article/jpi1958/21/6/21_6_410/_pdf

Hiroshi Ito

Papers

The Epoxidation of Dimers Obtained from Diels-Alder Reactions between Cyclopentadiene and Butadiene