An Efficient Synthesis of Bis-indolylindane-1,3-diones, Indan-1,3-diones, and Indene-1,3(2H)-denies Using [Hbim]BF₄ Ionic Medium

Table 1

Synthesis of bis-indolylindane-1,3-dione, 2-(1′,3′-dihydro-1H-[2,3′]biindolyl-2′-ylidene)-indan-1,3-diones in the presence of [Hbim]BF₄ ionic medium.

Entry	R^1	R^2	R^3	Product	Time (min)	Yield (%)^a	Melting point
							Report, m.p. (°C)	Li. m.p. (^°C) [Ref]
1	H	H	H	3a	5	95	207–209	208–210 [9]
2	H	H	F	3b	10	90	121–123	Prepared for the first time
3	H	H	Br	3c	8	93	105–107	104–106 [9]
4	H	CH3	H	3d	4	97	107–109	108–110 [9]
5	CH3	H	H	3e	3	97	233–235	232–234 [9]

aYield refers to pure products after crystallization.