4-arylmethylene-5 -oxazolones

The outcome of Grignard reactions on 5(4H)-oxazolones likewise depends on the nature of the substituent at C(4). The saturated azlactone (210) is converted by the action of phenylmagnesium bromide into the tertiary acylamino alcohol shown in equation (48) on the other hand, saturated azlactones are obtained by the action of alkyl Grignard reagents on (arylmethylene)oxazolones (equation 49). This type of oxazolone reacts with arylmag-nesium halides at the carbonyl group in the presence of copper chloride, however, the addition is directed to the methylene carbon atom. 

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... 

Table 41 Reaction of (Z)-4-arylmethylene-5(4H)-oxazolones with hydrazides to give substituted 1,2,4-triazole derivatives (Equation 61)...

Extension of this reaction to other 4-arylmethylene-5(4//)-oxazolones and a careful study of the cyclopropanation of (Z)-4-(ethylidene)-2-phenyl-5(4//)-oxazo-... 

Diphenyldiazomethane has also been used in 1,3-dipolar cycloadditions with 4-arylmethylene-5(47/)-oxazolones 670 to prepare gem-diphenyl-spirocyclopropane oxazolones 671." A number of 671 analogues were evaluated as antibacterial agents. " In addition, 671 derivatives were precursors for new 1-aminocyclopropanecarboxylic acid derivatives 672, for example, l-(benzoylamino)triphenylcy-clopropanecarboxylic acid 672 (R = Ar = Ph) (Scheme 7.211). 

The reaction of nitrile oxides with 4-arylmethylene-5(4//)-oxazolones 675 to give the corresponding spiroisoxazoline oxazolones 676 is also well known.The regiochemistry of this cycloaddition reaction was initially incorrectly assigned but a careful study of the reaction showed that the regiochemistry of the 1,3-dipolar cycloaddition of nitrile oxides is the same as that observed with nitrile imines (Scheme 7.213). Examples of spiroisoxazoline oxazolones are shown in Table 7.49 (Fig. 7.60). 

The 7i-donor behavior of 4-arylmethylene-2-phenyl-5(47/)-oxazolones 762 with the 7i-acceptor tetracyanoethylene has also been studied. The initially formed charge-transfer complex is converted via intermediate 763 to a new compound for which a 2-aryl-l-benzamido-3,3,4,4-tetracyanocyclobutanecarboxylic acid 764 has been proposed on the basis of the NMR spectral data (Scheme 7.233). Charge-transfer complexes of 2-aryl-4-arylidene-5(47/)-oxazolones with di- and trinitrobenzene as n acceptors have also been prepared. ... 

The Erlenmeyer reaction has also been used to prepare new 4-arylmethylene-2-[3-chlorobenzo[Z ]thien-2-yl]-5(4//)-oxazolones 800 from the appropriate A-acylgly-cine 799 and several aldehydes (Scheme 7.244). °° The pharmacological activity of these compounds as antibacterial and antiinflamatory agents has been studied. 

Similarly, 4-(furan-2-ylmethylene)-2-phenyl-1 -substituted-5(477)-imidazolones 820, evaluated as antibacterial and antifungal agents, have been synthesized from the 4-(furan-2-yhnethylene)-2-phenyl-5(4//)-oxazolone 819 (Scheme 7.253). ° Using 4-arylmethylene-2-phenyl-5(4//)-oxazolones as substrates and 2-amino-5-methyl-l,3,4-thiadiazoles as nucleophiles the synthesis of the corresponding... 

A new method for the synthesis of 4(3//)-qumazolinones 822 and 1,4-benzo-diazepine-2,5-diones 823 from reaction of 4-aryhnethylene-2-methyl- 821 (Rj = Me) or 4-arylmethylene-2-phenyl-5(4/i/)-oxazolones 821 (Rj = Ph) with o-aminobenzamide has also been reported (Scheme 7.254). ... 

These same authors described the reaction of 4-arylmethylene-5(4//)-oxazolones 824 with 2-(o-aminophenyl)benzimidazole to produce a mixture of substituted benzimidazo[l,2-c]quinazolmes 825 and 826 (Scheme 1.255) ... 

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). 

Arylmethylene-5(2i/)-oxazolones, unsaturated pseudooxazolones , are prepared by the combined action of acetic anhydride and pyridine on a-(/3-chloroarylacetyl) amino acids (equation 159) or on a-acryloylamino acids (equation 160). 

Arylamines ring-open 2-aryl-4-arylmethylene-5(4//)-oxazolones (179) to give arylamides of a-arylcarboxamido- -arylacrylic acids which sometimes recyclize to form imidazolones (Scheme 120)... 

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