2-Methyl-4-benzyl-5-oxazolone

Methyl-4-benzyl-6-oxazolone. ° Five grams of powdered phenylalanine is heated at 100° for five minutes with 50 cc. of acetic anhydride. The mixture is shaken vigorously during the heating. Acetic acid and cetic anhydride are removed under reduced pressure, and the residue is fractionated, yielding 3.1 g. (54%) of 2-methyl-4-benzyl-n5-oxazolone, b.p. 118°/0.8 mm. 

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... 

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. 

The use of chiral organometaUic compounds as catalysts in the enantioselective hydrolysis of saturated oxazolones was reported several years ago and the mechanism of the hydrolysis of 4-benzyl-2-methyl-5(4//)-oxazolone catalyzed by the copper(II) complex of (5)-[(A-benzylprolyl)amino]benzaldoxime has been described. ... 

It is well known that hydrogenation of dehydroamino acid derivatives derived from ring opening of unsaturated 5(4H)-oxazolones affords new racemic amino acids and, in some cases, enantiomerically pure compounds. On the other hand, a number of attempts have been made to hydrogenate the double bond of the unsaturated oxazolone itself. For example, 4-benzyl-2-methyl-5(4//)-oxazolone was prepared from 4-benzylidene-2-methyl-5(4H)-oxazolone using Raney Ni as a catalyst. This process is reported to be a general procedure to prepare saturated oxazolones directly (Scheme 7.194). 

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... 

Treatment of saturated azlactones with aromatic compounds under Friedel-Crafts conditions gives acylamino ketones in high yield (equation 46). 4-Benzyl-2-methyl-5(4H)-oxazolone undergoes an intramolecular reaction to yield an acetamidoindanone (equation 47). Friedel-Crafts reactions of 4-(arylmethylene)-5(4H)-oxazolones are complicated by the presence of an additional electrophilic centre (cf. 201) and may follow three courses. The unsaturated azlactone (189) adds benzene under the influence of aluminum chloride to form the saturated azlactone (207) in inert solvents (189) undergoes an intramolecular acylation to yield a mixture of the indenone (208) and the isoquinoline (209 Scheme 20). 

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... 

Benzyl.4.benzyliden.oxazolon-(S) 27, 226. 2-PhenyI.4-[4-methyl-benzyUden]-oxazo lon.(5) 27 I 299. 

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