http://rhodium.lycaeum.org (http://rhodium.lycaeum.org)
http://home.ici.net/~hfevans/reactions/RXN300.htm (http://home.ici.net/~hfevans/reactions/RXN300.htm)
but instead the new carbon-carbon bond is formed between the formaldehyde imine and the 2-position of the indole nucleus.