A mild synthesis of bis(indolyl)methanes using a deep eutectic solvent

摘要

Deep eutectic solvents (such as the combination of urea and choline chloride) are effective solvents/ organocatalysts for the condensation of indole and aryl or alkenyl aldehydes to form bis(indolyl)meth-anes. The reaction conditions are quite mild and do not require additional Bronsted or Lewis acid catalyst, though they fail with ketones or aliphatic aldehydes. Given the inexpensive, non-toxic, and recyclable nature of the DES, these reaction conditions are simple and highly environmentally friendly.