4.4- dimethyl-2-phenyl-5 -oxazolone

Reaction of hippuric acid and A, A -dimethylacetamide in the presence of phosphorous oxychloride affords 4-[l-(dimethylamino)ethylidene]-2-phenyl-5(4//)-oxazolone 424 " ° that is converted to 4-benzoylaminopyrazolones 425 via ring opening and cyclization with hydrazines (Scheme 7.139). " ° 4-(A, Af-Dimethyl-aminomethylene)-2-substituted-5(477)-oxazolones react similarly. 

Bromo-1 -(dimethylaminoethylidene)] -2-phenyl-5(47/)-oxazolone 426, obtained by bromination of 424, reacts with A, Al-dimethyl-Al -heteroarylformamidines to afford the interesting heterocyclic unsaturated oxazolones 428 (Scheme 7.140). ... 

Z)-4-[(5)-2,2-Dimethyl-l,3-dioxolan -ylmethylene]-2-phenyl-5(47/)-oxazolone 632 can react as a dienophile in diastereoselective Diels-Alder reactions. Thus, 632 undergoes a thermally induced Diels-Alder reaction with cyclic dienes, for example, cyclopentadiene and cyclohexadiene, to afford a mixture of the four... 

The X-ray crystal structure of fZ)-4-[(5)-2,2-dimethyl-l,3-dioxolan -ylmethyl-ene]-2-phenyl-5(4//)-oxazolone has been determined. " The analysis shows an almost planar disposition for the entire molecule with the exception of the dioxolane ring that adopts an envelope conformation. As such, the dioxolane ring is mainly situated on the si,si diastereotopic face of the olefinic bond, a situation that accounts for the observed diastereoselectivity in Diels-Alder reactions. 

Benzoylamino-6 -pyrido[l,2-a]pyrimidin-6-one 224 was prepared starting from 2-methylpyrimidine and N.TV-dimethylformamide dimethyl-acetate in boiling dimethylformamide (91BSB533). Then the resulting 2-[( )-2-(N,N-dimethylamino)ethenyl)]pyrimidine was reacted with 2-phenyl-5(4//)-oxazolone in refluxing acetic acid to give 6-oxopyrido-[l,2-a]pyrimidine 224 in 33% yield. 

Sustmann, R. Korth, H. G. Carbonsaure-, Thiocarbonsaurehalogenide bzw. Carbon-saure-halogenid-imide. Houben-Weyl, Metho-den der Organischen Chemie 1985, E5, 589. Smith, C. W. Rasmussen, R. S. Spectroscopic evidence concerning the structure of 2-phenyl-4,4-dimethyl-5(4)-oxazolone hydrobromide. 

The reaction of 2-phenyl-5(4//)-oxazolone and 4-[2-( )-dimethyl-aminoethenyl]-6-raethyl-2-methoxypyrimidine in boiling acetic acid afforded 7-benzamido-3-methyl-l-methoxy-8//-pyrido[l,2-c]pyrimidin-8-one (91BSB533). 

The 2-oxazolin-S-ones are excellent acylating agents for a variety of enzymes. Thus, 2-phenyloxazolin-5-one and 4,4-dimethyl-2-phenyl-2-oxazolin-S-one react with a-chymotrypsin, trypsin, and papain to form stable acyl enzymes.15-18 The azlactone from p-nitrobenzoylvaline reacted with a-chymotrypsin and trypsin, and it was observed that the enzymic activity of chymotrypsin decreased with increasing number of p-nitrobenzoylvaline residues.19 The reaction of a-chymotrypsin with 2 has been studied extensively.20-25 In this reaction, the oxazolone dis-... 

Phenyl-4-[3.5 dimethyl-4-(/5 carb6thoxy-cyan-vinyl) -pyrry 1- (2). metbyien]-oxazolon-(5) 27 II845. 

Phenyl-4- [2.5-dimethyl-l -phenyl-4-oarb= athoxy-pyrry 1.(3)-methylen j-oxazolon-( 5) 27 II 832. 

---