A convenient, eco-friendly, and efficient method for synthesis of bis(3-indolyl)methanes “on-water”

Figures & data

Scheme 1.  “On-water” synthesis of bis(3-indolyl)methanes.

Table 1. Synthesis of bis(3-indolyl)methanes in water.

Entry	Indole 1	Aldehydes 2	Product 3 ^a	Catalyst	Yield (%)^b; melting point (°C)^a
1			3a	Without external catalyst	80; 89–91 [Ref. 31, 88–90]
2			3b	Without external catalyst	78; 93–95 [Ref. 32, 94–96]
3			3c	Without external catalyst	75; 117–118 [Ref. 33, 117–118]
4			3d	Benzoic acid (5 mol%)	76; 187 [Ref. 32, 187–189]
5			3e	Benzoic acid (5 mol%)	75; 196–198 [Ref. 31, 198–200]
6			3f	Benzoic acid (5 mol%)	83; 94–96 [Ref. 31, 97–99]
7			3g	Benzoic acid (5 mol%)	90; 75 [Ref. 32, 76–77]
8			3h	Benzoic acid (5 mol%)	92; 108–110 [Ref. 17, 110–112]
9			3i	Benzoic acid (5 mol%)	91; 215–217 [Ref. 32, 217–219]
10			3j	Benzoic acid (5 mol%)	92; 220 [Ref. 31, 218–220]
11			3k	Benzoic acid (5 mol%)	85; 124–125 [Ref. 35, 126–127]
12			3l	Benzoic acid (5 mol%)	78; 169 [Ref. 24, 168–170]
13			m	Benzoic acid (5 mol%)	80; 231–233 [Ref. 34, 233–234]
14				Without external catalyst	83; 246–248 [Ref. 35, 247–248]
15				Without external catalyst	78; 173 [Ref. 35, 174–175]
16				Benzoic acid (5 mol%)	88; 226–228
17				Benzoic acid (5 mol%)	90; 238–239
^aAll products were identified by their melting points and spectral data.
^bIsolated yields after column chromatography.

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