A practical synthesis of bis(indolyl)methanes employing boric acid

A variety of aldehydes and ketones react rapidly with indoles in the presence of boric acid under solvent-free conditions to afford the corresponding bis(indolyl)methanes. Excellent yields and short reaction times together with the environmentally friendly nature of boric acid make this procedure useful and attractive to produce a variety of bis(indolyl)methanes. The use of boric acid makes it quite simple, more convenient, and practical. This new method offers several advantages such as high conversions, cleaner reaction profiles, short reaction times, and the use of inexpensive and readily available boric acid.