1,2-Epoxy cyclohexane preparation

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

Characteristics of Epoxy Networks Prepared with Hexane and Cyclohexane via CIPS. 

Fig. 23a. SEM micrographs of macroporous epoxy networks prepared via CIPS with 15 wt % cyclohexane at a curing temperature of 40 °C. Reprinted from Polymer, 37(25). J. Kiefer, J.G. HUborn and J.L. Hedrick, Chemically induced phase separation a new technique for the synthesis of macroporous epoxy networks p 5721, Copyright (1996), with permission from Elsevier Science...

Fig. 23b. SEM micrographs of macroporous epoxy networks prepared via CIPS with 20 wt % cyclohexane at a curing temperature of 40 °C...

Fig. 36. Density of epoxy networks prepared via CIPS with cyclohexane before and after the drying procedure...

The numerical simulations of the stress distributions are carried out on porous materials submitted to uniaxial loading. In order to check the validity of the numerical simulations, macroporous epoxies are prepared via the CIPS technique. Cyclohexane is selected as the solvent, thus resulting in the formation of a closed porosity, and the statistical distribution of the voids coincides with the random distribution of the model system. The structural characteristics of these materials prepared by curing at T=80 °C are summarized in Table 4. 

Various types of crack propagation, namely unstable, partially stable, and fully stable can be observed during SENB tests [85,131]. Solvent-modified epoxy networks prepared via CIPS with 13-16 wt % and 22 wt % cyclohexane show unstable crack propagation. For solvent-concentrations of 18 wt % and 20 wt % cyclohexane, a partially stable crack propagation is observed. The amount of energy consumption upon crack propagation is only 10% and 14% respectively for these two compositions. The change in the fracture behavior indicates that the... 

Fig. 46. a Critical stress intensity factor, of solvent-modified and macroporous epoxy networks prepared via CIPS with various amounts of cyclohexane, b Fracture energy of sol-vent-modified and macroporous epoxy networks prepared via CIPS with various amounts of cyclohexane... 

Fig. 47. Load-displacement curves of solvent-modified and macroporous epoxy networks prepared with 20 wt % cyclohexane via CIPS with SENB testing at 1 mm/min...

A total synthesis of the natural product cyclophellitol, 38, a P-glucosidase inhibitor, has been described starting from >-glucose, in which the key transformations are Fenier rearrangement of 35 and a stereoselective epoxidation of 37 (Scheme 10). The natural product (-)-ovalicine 39, another epoxy cyclohexane, has been prepared from the cyclitol L-quebrachitol (Scheme 11). ... 

Amine curatives useful in imparting chemical resistance to epoxy adhesives have been described in a recent patent issued to Takeda Chemical Industries, Ltd. These curatives are aldimized or ketimized derivatives of l,3,5-tris(aminomethyl)benezene or cyclohexane, prepared by condensation of the polyamine with an appropriate aldehyde or ketone (Eq. 10) and are... 

The synthesis of the trisubstituted cyclohexane sector 160 commences with the preparation of optically active (/ )-2-cyclohexen-l-ol (199) (see Scheme 49). To accomplish this objective, the decision was made to utilize the powerful catalytic asymmetric reduction process developed by Corey and his colleagues at Harvard.83 Treatment of 2-bromocyclohexenone (196) with BH3 SMe2 in the presence of 5 mol % of oxazaborolidine 197 provides enantiomeri-cally enriched allylic alcohol 198 (99% yield, 96% ee). Reductive cleavage of the C-Br bond in 198 with lithium metal in terf-butyl alcohol and THF then provides optically active (/ )-2-cyclo-hexen-l-ol (199). When the latter substance is treated with wCPBA, a hydroxyl-directed Henbest epoxidation84 takes place to give an epoxy alcohol which can subsequently be protected in the form of a benzyl ether (see 175) under standard conditions. 

As shown in Eq. 9.48, optically active alkylidene lactones having an iodoalkyl substituent were prepared from the corresponding optically active epoxy alcohol by means of the Sharpless epoxidation. These represent precursors of optically active functionalized cyclopentanes and cyclohexanes, respectively, as shown in the equation [92]. 

Fig. 24. Pore size distributions of macroporous epoxies prepared via CIPS with cyclohexane obtained from image analysis...

Figure 45 shows the glass transition temperature of solvent-modified networks prepared with various amounts of cyclohexane. It is seen, that Tg is independent of, or varies only slightly with, the initial amount of cyclohexane after the heat treatment. The T -values of solvent-modified epoxy networks are lower than for the fully crosslinked network, which is a result of the cyclohexane dissolved in the matrix, with a concentration given by the binodal curve and therefore is independent of the initial amount of cyclohexane. 

Fig. 49. Load-displacement curves of solvent-modified, semi-porous, and macroporous epoxies prepared with 22 wt % cyclohexane via kinetically controlled CIPS with 1 wt % catalyst...

As for the samples prepared without catalyst, the ability for energy absorption after crack propagation decreases strongly as the solvent is removed. This is reflected in Fig. 49, where the load displacement curves of solvent-modifled, semi-porous, and macroporous epoxies prepared with initially 22 wt % cyclohexane (( )=18.5%) are shown. The crack length is the same in all three cases. Therefore the decrease in maximum load is directly proportional to the decrease in Kj. It is also clearly seen that the fracture behavior changes drastically and that the surface under the load-displacement curve, which is used to calculate the fracture energy is signiflcantly lowered. 

Experimentally a cyanate ester precursor mixture consisting of BPEC, 1 wt % BPE, and 100 ppm cobaltacetylacetonate was prepared and subsequently mixed with the cyclohexane phase separating solvent [86]. Essentially the same procedure as for the epoxy is used for sample preparation with the difference that the curing was done at 80 °C and post drying at 240 °C. 

The melting enthalpy related to the sample mass, represented by the area of this melting peak, increases nearly Hnearly with increasing amount of solvent once phase separation has occurred (Fig. 54). The appearance of such a melting peak has also been observed for cyclohexane-modified epoxies prepared with more than 20 wt % cyclohexane, having domain sizes larger than around 5 pm and a volume fraction of higher than around 13%. 

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],... 

Block polymers were prepared by organolithium-initiated polymerization in cyclohexane solution by using the sequential monomer addition technique (3). Polymers were both of the linear-SBS and radial -branched (SB) type. Blends were prepared in cyclohexane solution, either before or after coupling the initially linear SBLi precursor. Coupling agents investigated were ethyl acetate (for linear coupling), epoxi-aized soybean oil (ESO), and SiCh. 

The prepared CECs are highly viscous liquids or solids with a softening temperature below 60 °C. The epoxy groups content is above 90% of the calculated value. The IR spectrophotometry confirms the occurence of imide rings (1785,1720 and 1420-1375 cm" ) and epoxy groups at cyclohexane ring (790-795 cm ). 

Other epoxides that have been reported to give a time-dependent inhibition are 2-methyleneoxide-(l,3,5/4,6)-pentahydroxy cyclohexane with sucrase-isomaltase and 1,2-epoxy-( -glucopyranosyl) ethane with /3-glucosidase from sweet almonds." Preparation of these two compounds in radioactive form has not been reported. 

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