2-styryl-5 -oxazolone

The same reaction applied to 2-styryl-5(4/l/)-oxazolone 282 gives simultaneous acylation and alkylation of the arene to produce the corresponding a-acylamino ketones 283. ° Cyclodehydration of 283 then readily affords a 2,5-disubstimted oxazole (e.g. 284 as shown in Scheme 7.92). 

Schiff bases also react with unsaturated 5(477)-oxazolones and afford different products depending on the substituent at C-2. With 2-methyl-5(477)-oxazolones 545 as starting materials, 2-styryl-l-substituted imidazolones 546 are obtained (Scheme 7.172). ° Selected examples are shown in Table 7.43 (Fig. 7.54). 

TABLE 7.43. 2-STYRYL-l-SUBSTITUTED IMIDAZOLONES FROM REACTION OF UNSATURATED 5(4ff)-OXAZOLONES WITH SCHIFF BASES... 

The phenyl group of trisubstituted 4-benzylidene-5(4//)-oxazolones is nearly planar whereas the styryl moieties in (Z)-2-phenyl-4-(a-phenylethylidene)-5(4//)-oxazolone and fZ)-2-methyl-4-(a-phenylethylidene)-5(4//)-oxazolone show significant deviations from planarity. ... 

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