La(OTf)3 facilitated self-condensation of 2-indolylmethanol: construction of highly substituted indeno[1,2-b]indoles.

The Lewis acid-promoted self-condensation of 2-indolylmethanols has been revealed. On treatment with La(OTf)3, highly substituted indeno[1,2-b]indole derivatives have been synthesized by using easily accessible 2-indolylmethanols with up to 94% yields. The utility of this method is further highlighted by evaluating the initial photophysical properties of some prepared products, indicating that the protocol may have potential applications in the construction of novel fluorescent materials.