1,2-Epoxy cyclohexane reactions

Note Use of epoxy cyclohexane in a ring opening reaction with imidazole invariably results in racemic N-hydroxy cyclohexyl imidazole. This of course presents a problem if the ligand is to be used in asymmetric catalysis. 

In reaction (22), the epoxy cyclohexane group is reactive under acidic conditions, whereas the epoxy ethyl group is reactive under basic conditions. The chemical structure shown is beUeved to be the predominant form of the reaction product. However, it should be observed that the reaction product very possibly may consist of a mixture of materials with varying structures. Thus, the reaction product may, in addition to the structure, may contain a product wherein the polysulfide oligomer chain or a portion of the reaction product has —SH terminals at both ends of the oligomer chain. 

Phase Separation Mechanism in Hexane-Epoxy Systems. . Influence of Reaction Parameters on the Morphology of Cyclohexane-Modified Epoxy Networks Prepared via CIPS... 

During synthesis of the hormone rf-aldosterone, 20,21-dihydroxy-lip,18-epoxy-5a-pregnan-3-one diacetate was oxidised to the 3-oxo acid by stoich. RuOy CCl [78, 79], Oxidation of a substituted pyrrolidine to a pyroglutamate, part of the total synthesis of the antibiotic biphenomycin B, was effected by RuO /aq. Na(lO )/ EtOAc [102], Oxidation of a number of A-5 steroids to enones was effected by RuClj/TBHP/cyclohexane [391] safety aspects of these large-scale reactions were examined, as in the preparation of the antibacterial squalamine [186],... 

Thus, the ring-opening reaction of l,2-epoxy-l-(4-nitrophenyl)cyclohexane (1) with boron trifluoride diethyl ether complex exhibits a pronounced solvent dependence as shown in Table 4.31... 

A solution of the steroid (50 mg, 0.12 mmol) in cyclohexane (10 ml) containing DIB (40 mg, 0.12 mmol) and iodine (28 mg, 0.11 mmol) was irradiated with two 100 W tungsten-filament lamps for 50 min at 40°C. The reaction mixture was poured into water and extracted with ether the organic layer was washed with aqueous sodium thiosulphate and then water, dried, concentrated and the residue was purified by column chromatography on silica gel (hexane-ethyl acetate, 9 1) to give 6/ ,19-epoxy-5a-cholestan-3/I-yl acetate (45 mg, 90%) m.p. 114-115°C. 

Finally, the Mannich reaction may be applied to the. synthesis of reactive amines used as crosslinking agents of epoxy resins. The process requires the availability of molecules possessing more than two NH groups, which are obtained by reaction of polyfunctional substrates with polyfunctional primary amines (oligomeric polyalkyle-ncamines, diamino cyclohexane, etc.) - (see also 422, Chap. Ill, C). 

Fig. 3. Efects of pH on reaction rates of epoxies. Cyclohexene oxide phenylglycidyl ether A vinyl cyclohexane oxide.

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