4-benzyl-2-phenyl-5 -oxazolone

Phenyl-4-benzyl-6-oxazolone. Ten grams of benzoyl-dl-/3-phenyl-alanine is heated on the steam bath for thirty minutes with 100 cc. of acetic anhydride. The solution is concentrated in vacuum, and the syrupy residue is dissolved in 100 cc. of petroleum ether, b.p. 60-110 . The solution is decanted from a small amount of insoluble material and is cooled. Practically pure 2-phenyl-4-benzyl-5-oxazolone crystallizes in long needles, m.p. 69-71° yield 7.5 g. (80%). 

Azlactones can be hydrolyzed to the corresponding acids with either alkaline or acidic reagents, the alkalies being conaderably more effeo- tive. The ease of the reaction depends to a marked extent upon the nature of the substituents on the oxazolone ring. Unsaturation in the 4-position or an aryl group in the 2-position stabilizes the mdecule. Thus 2-methyl-4-benzyl-5-oxazolone is hydrolyzed by water at room temperature, 2-methyl-4-benzal-5-oxazolone by boiling aqueous acetone, and 2-phenyl-4-benzal-5-oxazolone by boiling 1% aqueous sodium hydroxide. ... 

Oxazol-5(2H)-one, 2-benzylidene-4-methyl-tautomerism, 6, 186 Oxazol-5(2ff)-one, 2-methylene-isomerization, 6, 226 Oxazol-5(2H)-one, 2-trifluoromethyl-acylation, 6, 201 Oxazol-5(4ff)-one, 4-allyl-thermal rearrangements, 6, 199 Oxazol-5(4H)-one, 4(arylmethylene)-Friedel-Crafts reactions, 6, 205 geometrical isomerism, 6, 185 Oxazol-5(4ff)-one, 4-benzylidene-2-phenyl-configuration, 6, 185 photorearrangement, 6, 201 Oxazol-5(4ff)-one, 4-benzyl-2-methyl-Friedel-Crafts reactions, 6, 205 Oxazol-5(4ff)-one, 4-methylene-in amino acid synthesis, 6, 203 Oxazol-5(4ff) -one. 2-trifluoromethyl-hydrolysis, 6, 206 Oxazolones... 

Alkylation of saturated 5(4//)-oxazolones at C-4 is a well-known reaction that can be achieved under a wide variety of conditions. Numerous articles have described this reaction as a means to prepare 4,4-dialkyl-5(477)-oxazolones 147 that are valuable intermediates to prepare ot,ot-disubstituted a-amino acids. For instance,2-phenyl-5(4//)-oxazolone 146 readily obtained from hippuric acid and A,A -dicyclohexylcarbodiimide (DCC), is alkylated at C-4 with allyl, benzyl, or phenacyl halides if the reaction is conducted in dipolar aprotic solvents in the presence of weak bases. Hydrolysis of the resulting 5(477)-oxazolones leads to a,a-dialkylglycines 148 (Scheme 7.43). 

A number of points should be considered to determine the most appropriate experimental conditions for the desired reaction and, to that end, the kinetics of hydrolysis and ionization of 4-methyl-2-phenyl-, 4-benzyl-2-phenyl-, and 4-benzyl-2-methyl-5(4//)-oxazolones have been investigated. Deprotonation of 5(477)-oxazolones in aqueous media, which leads to racemization of optically active 5(477)-oxazolones, is a fast process that competes with the ring opening. The difference between the rate constant for racemization and the ring opening is greater in solvents with dielectric constants less than water and thus, oxazolones racemize faster than they hydrolyze. 

Dimerization of 5(4//)-oxazolones affords two different products depending on the reaction conditions. In one case, 4-benzyl-2-phenyl-5(4F/)-oxazolone 291 was converted to the pyrrolidinedione 292 with potassium carbonate followed by acidic hydrolysis (Scheme 7.96). ... 

Finally, new palladium(II) and platinum(II) complexes from 4-benzyl-4-methyl-2-phenyl-5(477)-oxazolone or C2 symmetric bis(oxazolone) ligands have been... 

Padwa and Hamilton examined other aziridines where the nitrogen was unsubstituted.43 44 cis-1,2-Diphenylaziridine (21) on refluxing with DMAD in benzene gave 85% of the adduct 22 DEAD was also used. tranj-2-Benzoyl-3-phenylaziridine (23) gave the pyrrole 24 with DMAD the latter was also synthesized from 4-benzyl-2-phenyl-5-oxazolone (26), via 25, which was oxidized with selenium dioxide to 24. 

While several optically active oxazolones have been prepared, these intermediates are likely to undergo racemization in peptide syn-thesis.67 68 Thus, 2-phenyl-L-4-benzyl-2-oxazolin-5-one (26) was synthesized, and its rate of racemization with nucleophiles such as p-nitro-phenoxide ion and phenylalanine methyl ester was studied. The rates of... 

By studying the ring opening of (rac)-2-phenyl-4-benzyl-5(4H)-oxazolone with butanol catalysed by CALB in organic media, it has been possible to correlate the protonation state of the enzyme with the enantioselectivity of the reaction [36]. The protonation state was controlled by the use of either organo-soluble bases or solid-state buffers of known pfC. Both triethylamine and the buffer pair CAPSO/CAPSO.Na [CAPSO = 3-(cyclohexylamino)-2-hydroxy-l-propanesulfonic acid] were found to increase the enantioselectivity of reactions catalysed by CALB and also the lipase from Mucor miehei. The effect of solvent, water activity and temperature on the enantioselectivity of reactions catalysed by lipases and hydroxynitrile lyases (enzymes that catalyse the addition of cyanide to aldehydes) has been reported [37]. 

Benzoyl-DL-phenylalanine allowed to react 24 hrs. at room temp, with the equimolar amount of dicyclohexylcarbodiimide in dioxane 4-benzyl-2-phenyl-5-oxazolone. Y ca. 100%. F. e. s. I. Z. Siemion and K. Nowak, Roczniki Chem. 34, 1479 (1960). 

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