Epoxides, vinyl synthesis

The UV-radiation curing technology is not restricted to the synthesis of clay-acrylate nanocomposites, but it can be extended to other types of polymer systems, such as crosslinked epoxides, vinyl ethers and interpenetrating polymer networks, as well as to other types of layered nanoparticles, such as superconductive nanofillers and magnetic particles. Future work should be... 

The (partial) description of the synthesis and coupling of the five fragments starts with the cyclohexyl moiety C —C. The first step involved the enantio- and diastereoselective harpless epoxidation of l,4-pentadien-3-ol described on p. 126f. The epoxide was converted in four steps to a d-vinyl d-lactone which gave a 3-cyclohexenecarboxylate via Ireland-CIaisen rearrangement (cf. p. 87). Uncatalysed hydroboration and oxidation (cf. p. 131) yielded the desired trans-2-methoxycyclohexanol which was protected as a silyl ether. The methyl car-... 

Another synthesis of the cortisol side chain from a C17-keto-steroid is shown in Figure 20. Treatment of a C3-protected steroid 3,3-ethanedyidimercapto-androst-4-ene-ll,17-dione [112743-82-5] (144) with a tnhaloacetate, 2inc, and a Lewis acid produces (145). Addition of a phenol and potassium carbonate to (145) in refluxing butanone yields the aryl vinyl ether (146). Concomitant reduction of the C20-ester and the Cll-ketone of (146) with lithium aluminum hydride forms (147). Deprotection of the C3-thioketal, followed by treatment of (148) with y /(7-chlotopetben2oic acid, produces epoxide (149). Hydrolysis of (149) under acidic conditions yields cortisol (29) (181). 

The Aggarwal group has used chiral sulfide 7, derived from camphorsulfonyl chloride, in asymmetric epoxidation [4]. Firstly, they prefonned the salt 8 from either the bromide or the alcohol, and then formed the ylide in the presence of a range of carbonyl compounds. This process proved effective for the synthesis of aryl-aryl, aryl-heteroaryl, aryl-alkyl, and aryl-vinyl epoxides (Table 1.2, Entries 1-5). 

Table 1.1 Synthesis of aryl-vinyl epoxides by use of chiral sulfide 1 a phosphazene base.

This strategy can be applied to the synthesis of vinylepoxides, since high enantioselectivity and good regioselectivity can often be obtained in asymmetric dihydroxylation of dienes, resulting in vinylic diols [24, 25], Transformation of the diols into epoxides thus represents an alternative route to vinylepoxides. This strategy was recently employed in the synthesis of (+)-posticlure (Scheme 9.6) [26]. 

Scheme 9.32 Synthesis of (S)-ibuprofen (69) from vinyl-epoxide 70 Ar = 4- BuC6H4.

The subsequent epoxidation of these in situ formed allylic tertiary alcohols yielded the corresponding syn-e oxy alcohols with high levels of diastereo- and enantioselectivity, thus providing a novel one-pot asymmetric synthesis of acyclic chiral epoxyalcohols via a domino vinylation epoxidation reaction (Scheme 4.17). ... 

Scheme 4.10 gives some examples of application of alkyne carboalumination in synthesis. The reaction in Entry 1 was carried out as part of a synthesis of the immunosuppressant drug FK-506. The vinyl alane was subsequently transmetallated to a cuprate reagent (see Chapter 8). In Entry 2, the vinyl alane was used as a nucleophile for opening an epoxide ring and extending the carbon chain by two atoms. In Entries 3 to 5, the vinyl alane adducts were converted to vinyl iodides. In Entry 6, the vinyl alane was converted to an ate reagent prior to reaction with formaldehyde. 

Chloro-substituted [Ipc]2BH derivatives have proven useful for enantioselective synthesis of vinyl epoxides.62... 

Organic Network Formers. As indicated above, an additional organic network can be built up by organic polymer synthesis within an inorganic network. The basic principles are shown in Equations 3 to 5 with a vinyl, methyl methacrylate and epoxide polymerization ... 

A Japanese patent72) claims the synthesis of thermally stable copolymers by free-radical terpolymerization of dialkylstannyl dimethacrylates, glycidyl methacrylate and vinyl monomers (vinyl chloride, styrene, vinyl acetate, etc.). The products contain 0.5 to 30% tin and 0.05 to 7 % epoxide oxygen. 

A range of reactions of 2-chlorocyclohexyl(dichloro)phosphine (60) with alcohols and epoxides has been described, largely with a view to the synthesis of polymer intermediates and flame-retardants.50 The copolymerization of dichloro(phenyl)-phosphine with styrene and vinyl butyl ether in the presence of maleic anhydride has been studied.61... 

---