Epoxides reaction with cyanate

The reaction of epoxide resins with dicyanates was investigated using a model system. The system consisted of phenyl glycidyl ether and cumylphenyl cyanate [67]. Three reactions proceeded in the system ... 

The cyanate and the epoxide network can be bound by the reaction of phenolic hydroxyls contained in the partially cyclotrimerized cyanate prepolymer with the epoxy groups. In the first stage, a prepolymer was obtained by heating a mixture of BPA monocyanate and dicyanate with Co naphthenate as a catalyst (Scheme 15). 

Construction of the simplest fused heterocyclic system that shows some anabolic activity starts by epoxidation of the olefin at C2 in 23-1 with peracetic acid buffered with sodium acetate (23-2) (Scheme 5.23). Reaction of this intermediate with potassium thiocyanate and phosphoric acid, essentially thiocyanic acid, leads to diaxial opening of the oxirane to form the 3a-hydroxy-2/8-cyanate 23-3. Treatment of the product with base leads to formation of the /3-thioepoxide 23-5. Formation of that product can be rationalized by assuming that the first step involves removal by base of a proton on the hydroxyl group. That alkoxide then proceeds to add to the cyano group at C2 to form a transient five-membered ring as in... 

The synthesis of (-)-A -acetyl-O-methylacosamine, " an amino sugar, is an interesting application of the process of cis-hydroxyamination catalyzed by palladium complexes of olefins developed by Trost and Sudhakar. Enantiomerically pure aldehyde 263 was first transformed to vinyl epoxide 264. The latter reacted smoothly with p-toluene sulfonyliso-cyanate in the presence of 1-3 mol% of palladium and 6-18 mol% of tiiisopropyl phosphite in THF at room temperature. As thermal reaction favored 0-aIkylation, these conditions led exclusively to A-p-toluenesulfonyl-2-oxazolidone 265 as shown in Scheme 60. 

A series of molybdenum-doped materials based on thermosetting cyanate ester and epoxy resins was prepared and tested as catalysts for the epoxidation of cyclohexene, styrene, 1-octene and propylene with tert-butyl hydroperoxide as oxidant Monomers with more than two functional groups yield highly stable catalysts that can be used in several consecutive reactions without any catalyst reconditioning step. Metal leaching strongly depends on the resin as well as the substrate. 

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