5-ethoxy-2-phenyloxazole

Hassner and Fischer ° also found that 5-ethoxy-2-phenyloxazole 15 (Ri = CgHs, R2 = H, R3 = OC2H5) reacted with diethyloxomalonate to give several products, 800-802, depending on the temperature (Scheme 1.220). In contrast, 2-ethoxy-5-phenyloxazole 15 (Ri = OC2H5, R2 = H, R3 = CgHs) reacted with diethyloxomalonate only in the presence of BF3 OEt2 to afford 803. 

Lewis acid catalysis was required for the reaction of 2-ethoxy-5-phenyloxazole... 

N-Substituted benzotriazole intermediate (77) is an excellant synthon for the synthesis of 2-ethoxy-2-vinylcyclopropanecarboxylate esters (78) [95JOC6], 1-Propargylbenzotriazole was reacted with bromoacetophenone to provide the novel 2-(benzotriazolomethyl)furan (80) in 60% yield [95JOC638]. Annelated N-aminotriazoles, on oxidation, are a good source of cyclic alkynes as illustrated for the reaction of aminotriazolotropone (80) with 4-phenyloxazole to generate the furyl[3,4-cf]tropone (82) from a Diels-Alder intermediate with facile loss of benzonitrile [94TL8421 ]. 

Draw structures for the intermediates and final products that are formed when (i) 4-phenyloxazole is heated with but-l-yn-3-one C6Hg02 (ii) 5-ethoxy oxazole is heated with dimethyl acetylenedicarboxylate CioHi20g. 

Amino-4-ethoxycarbonyl-3-phenylisoxazole (114) similarly photo-isomerizes in the presence of triphenylene to give 5-amino-4-ethoxy-carbonyl-2-phenyloxazole.179... 

Treatment of 176 (Ar = CsHs) with iV-iodosuccinimide affords 5-ethoxy-4-iodo-2-phenyloxazole 178, from which the 4-alkynyl analogs 179 were obtained via... 

There is a single example of a cycloaddition involving an oxazole and a hyd-antoin. Thus 5-ethoxy-2-phenyloxazole 231 and hydantoin 232 reacted in refluxing xylene for 22 h to provide a 3 2 mixture of cis- and trans-22ii in 50% overall yield... 

Reaction of 5-ethoxy-2-phenyloxazole 231 with diethyl ketomalonate was reported by Hassner in 1989 (Fig. 3.70). " At 80°C, the 2,4,5-trisubstituted oxazole... 

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