Phenol ring opening

Irradiation/sodium hydroxide Photochemical phenol ring opening... 

Cuprous chloride pyridine Oxidatiye phenol ring opening C... 

The ring opening reactions of N-alkylideneaziridines, e.g. (313), with hydrogen, dilute hydrochloric acid and phenol have also been reported and are outlined below (80AG(E)276). 

The polybenzoxazines (PBZs) provide a new class of phenolic resins that were first described by Ishida in 1998 (Ref. 15). Synthesis of the resins involves three components a phenol, a primary amine and formaldehyde. The first stage involves the formation of a multifunctional benzoxazine monomer Figure 23.30 a)). The monomer can then be ring-opened at elevated temperatures (160-220 C) to yield a polymeric stmcture (Figure 23.30(b)). 

Biernath et al. concluded that phenolic novolac and epoxidized cresol novolac cure reactions using triphenylphosphine as the catalyst had a short initiation period wherein the concentration of phenolate ion increased, followed by a (steady-state) propagation regime where the number of reactive phenolate species was constant.85 The epoxy ring opening was reportedly first order in the steady-state regime. 

For commercial application, diepoxides such as those derived from bisphenol A are employed, and they are cured via ring-opening crosslinking reactions, into which the epoxy group enters readily. Bisphenol A is so-called because it is formed from two moles of phenol and acetone (Reaction 1.7). 

When excess amounts of the HHT of phenyl glycinate 42 were used with diphenyl phosphite, the preferred product was the novel cyclic derivative 45 (2). Presumably, ring-opening of the HHT produced intermediate 43 first, which lost an equivalent of glycinate formaldimine to give 44. The proximity of the activated phenyl carboxylate ester to the N-H in 44 presumably promoted intramolecular cyclization to 45 with loss of phenol (2). 

In the presence of cyclohexyl amine the photolysis of the dienone (58) gives the cyclohexyl amide expected from dienone ring fission and reaction of cyclohexyl amine with the ketene. However, in the presence of weaker nucleophiles the ring opened product is not trapped and instead there is a relatively slow formation of phenols<36,44) ... 

Alkylations of phenols with epichlorohydrin under PTC conditions and microwave irradiation were described twice in 1998. Subsequently, ring-opening reactions of the epoxide group were also performed using microwaves (Eqs. 20 and 21) [31, 32]. In the first catalytic synthesis of chiral glycerol sulfide ethers was described [31] in the second biologically active amino ethers were prepared [32],... 

The electrocydic ring opening of the cydobutene 196 at 140 °C in 1,4-CHD produced in situ the enyne-allene 197 (Scheme 20.41) [78]. Cycloaromatization to the biradical 198 followed by hydrogen-atom abstractions then produced the phenol 199. 

A large variety of metabolic cyclization reactions, counterparts to the reactions of hydrolytic ring opening discussed above, occur without any change in the degree of oxidation, and often nonenzymatically. Such reactions proceed by various mechanisms of intramolecular nucleophilic substitution, with elimination of amine, phenol, halide, or H20. 

Kinetic studies of various systems have been carried out as follows the reaction of 2,2 -dichlorodiethyl sulfide and of 2-chloroethyl ethyl sulfide with diethylenetriamine and triethylamine in 2-methoxyethanol ° the catalysed reactions of substituted phenols with epichlorohydrin the reactions of para-substituted benzyl bromides with isoquinoline under high pressure the reactions of O-alkylisoureas with OH-acidic compounds [the actual system was N, N -dicyclohexyl-0-(l-methylheptyl)isourea with acetic acid] and tlie ring opening of isatin in aqueous binary mixtures of methanol and acetonitrile cosol vents. 

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