Carbonylation aryl urea derivatives

An interesting oxidative carbonylation of anihne derivatives was pubhshed in 2009 [37]. The reaction proceeded under 1 bar of CO at room temperature with 5 mol% of [Pd(OTs)2(MeCN)2] as the precatalyst. Either cyclic imidates or methyl anthranilates can be easily generated, depending on the reaction conditions. The use of A -aryl urea derivatives with a terminal N-H moiety allowed for the generation of quinazolinones (Scheme 6.10). 

Booker-Milburn and Lloyd-Jones in 2009 revealed the cationic palladium-catalyzed carbonylation of aryl urea derivatives at room temperature under 1 atm of CO forming the cyclic imidates [31]. Key features of this procedure are the utilization of the Pd(OTs)2(MeCN)2 as the catalyst precursor and the powerful activating effect of the aniline -urea moiety in contrast with acetanilide (0% yield). For the A/ ,A/ -disubstituted substrates (Table 15.23), the yields were dropping with the steric bulk increasing, whereas for the AT-monosubstituted analogs, the trend was opposite. Prolonged reaction time resulted in low yields which can be rationalized by the reflection that the imidate products were sensitive to the added acid. 

Table 15.23 Represented products for the carbonylation of aryl urea derivatives. ...

The reaction of -halo carbonyl compounds with primary amides is appropriate for oxazoles containing one or more aryl groups . Ureas form 2-aminooxazoles. Formamide can be used resulting in a free 2-position in the oxazole. A convenient synthesis of 5-substituted-4-cyanooxazoles 223 is based on the condensation of -hydroxy—cyanoenamines 222 with trimethyl orthoformate (Scheme 109). The cyanoenamine intermediates 222 are derived from Lewis acid-catalyzed Passerini reactions between /-butyl isonitrile and aldehydes <2002S1969>. 

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