High-temperature transformation basic conditions

The mechanism inevitably involves the loss of water and, remarkably, methane. The yields are usually low due to the high temperatures required for this transformation to occur. If the 1,2-dihydroquinoline is isolated the aromatization can be performed in a separate step under acidic or basic conditions. ... 

The results of the thermolyses demonstrate the potential of high-temperature water for the study of biomimetic transformations. Furthermore, they confirm that for certain reactions, elevated temperatures under neutral pH conditions can offer advantages over the use of more acidic (or basic) reagents at lower temperatures. Some microwave-assisted reactions proceed rapidly, in the presence of (i) less catalyst, (ii) a milder catalyst or, (iii) no added catalyst, as found here. 

Among the different methods for controlling competing transformations in the interaction between 2-benzopyrylium salts and ammonia (such as varying temperature in the different steps of reaction and using different solvents), the most effective is the application of acid catalysis, and the best experimental condition is heating the mixture of 2-benzopyrylium salt and ammonium acetate in acetic acid. In this case, the high selectivity of the whole process is determined by the weak nucleophilicity and basicity... 

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