Indole-2-carboxylic acid, flash vacuum pyrolysis

Flash vacuum pyrolysis of 2-methoxycarbonylpyrrole (11) gives the ketene (12), characterized by IR absorption at 2110 cm. On warming to -100 to -90 °C the dimer (13) is formed (82CC360). Flash vacuum pyrolysis of indole-2-carboxylic acid (14) results in loss of water and the formation of a ketene (15) showing absorption at 2106 cm (82CC360). 

The use of flash vacuum pyrolysis of 3-hydroxypyridine-2-carboxylic acid 348 to obtain the symmetrical dipyr-rolo[ 1, 2-a 1, 2 - ]pyrazinc-5,10-dione 352 is noteworthy <2002TL5285> and has been used to generate the corresponding indole-containing diketopiperazine <20030BC2168> (Scheme 26). 

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