2-amino-5- -4-methyloxazoles

Amino-3-methylisoxazole, 1502 2-Amino-4-methyloxazole, 1500 5-Amino-3-methylthio-l,2,4-oxadiazole, 1192 Ammonium A-nitrosophenylaminooxide, 2399 2-Aza-l,3-dioxolanium perchlorate, 0898 Azoformaldoxime, 0815 Bis(l-benzo[d]triazolyl) carbonate, 3598 Bis(l-benzo[d]triazolyl) oxalate, 3629 Bis(trifluoromethyl) nitroxide, 0638 2-/er/-Buty 1-3 -phenyloxaziridine, 3406 Calcium bis(O-hydroxylamide). 3930 Calcium hydroxide O-hydroxylamide, 3929... 

See Hydrogen peroxide 2-Amino-4-methyloxazole See related ISOXAZOLES... 

Reactions of Oxazoles. 2-Amino-4-methyloxazole (359) forms the rearranged hydro-peroxide (360) by the action of hydrogen peroxide. Thermolysis of 2- (3,3-di-methylallyloxy)-4,5-diphenyloxazole yields the oxazolin-2-one (361) with inversion of the allyl group by [ , ] sigmatropic shift irradiation, on the other... 

Khan and Crank found this same pattern of reactivity with condensations of 2-amino-4-methyloxazole 622 (X = 0, R = CH3) with aromatic aldehydes. The authors did not see any evidence for the expected Schiff base. Instead, they isolated products of hydroxymethylation at C(5) 625 in good yield (Scheme 1.172). The structure of 625 (X = O, R = CH3, Ar = 4-CH3OC6H4) was confirmed by X-ray... 

TABLE 1.46. 2-AMINO-5-(HYDROXYMETHYL)-4-METHYLOXAZOLES FROM 2-AMINO-4-METHYLOXAZOLES AND ALDEHYDES-... 

Mekonnen and Crank also found the same reaction dichotomy in Friedel-Crafts reactions of 622 (X = O) with acid chlorides or acid anhydrides. In general, acylation of 622 (X = O, R = CH3) with acetic anhydride or benzoyl chloride/ pyridine afforded the corresponding 2-(acylamino)-4-methyloxazole 630a and 630b (Scheme 1.174). However, low-temperature acetylation or aroylation of 622 (X = O, R = CH3) in the presence of two equivalents of AICI3 produced a 5-acyl-2-amino-4-methyloxazole 631 in low to modest yield. The authors reported that AICI3 was the most effective Lewis acid (SnCLj and TiCL) and that the reaction required two equivalents of Lewis acid. Selected examples are shown in Table 1.48. 

Compared to the Diels-Alder reactions of 5-alkoxyoxazoles, relatively few examples exist for intermolecular cycloadditions of aminooxazoles and their derivatives. Since the initial studies of 5-aminooxazoles by Kondrat eva only four others have been reported. 2-Amino-4-methyloxazole 66a reacted with diethyl maleate at room temperature in ethanol to provide a 35% yield of 67 and 11% of 68 (Fig. 3.19). The acetamide derivative 66b reacted with maleic anhydride at 50°C in toluene to give only the decarboxylated 3-hydroxypyridine 69. 

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