2- -5-methoxy-4-methyloxazole

Vilsmeier formylation of 4-methyloxazole gives a 1 1 mixture of 2- and 5-formyl derivatives (94H1791). A formal [2+3] cycloaddition of benzaldehyde to the 5-methoxy-oxazole 30 (R = p-MeOC H4), catalyzed by methylaluminium di(0-naphthoxide), affords the oxazoline 31 with 98% cis-selectivity, while the trans-isomer is produced in the presence of titanium(IV) chloride or tin(IV) chloride (93JOC7397). 

Irradiation of a methanolic solution of an oxazole at —78°C in the presence of O2 and rose bengal produced a 2,5-disubstituted 5-hydroperoxy-4-methoxy-4,5-dihydrooxazole 709 (Scheme 1.197). Here again, the oxazole substitution pattern determined the product distribution. For example, 4,5-diphenyl-2-methyloxazole 231a produced only N, iV-dibenzoyl acetamide 706 (Ri = CH3, R2 = R3 = CeHs). On the other hand, 4-methyl-2-phenyloxazole 701a gave 709 (Ri = CgHs, R2 = CH3, R3 = H), which decomposed on warming to room temperature to yield... 

Quinones have been shown to react with 5-aIkoxyoxazoles to yield hydroxypyr-idines. The isoquinolinequinone 60 was prepared in 60% yield from 4-ethyl-5-methoxy-2-methyloxazole 58 and the quinone 59 in benzene at 60°C for 30 h (Fig. 3.17). 3... 

Benoit et al. (2008) studied the large-scale preparation of 2-methyloxazole-4-carboxaldehyde. They have described a method for the preparation of 10 Kg batches of 2-methyloxazole-4-carboxaldehyde. Here, reduction of the corresponding N-methoxy-N-methyl amide to the corresponding aldehyde using lithium aluminum hydride has been reported followed by workup and isolation by crystallization. 

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