A convenient procedure for accessing a,a-bis(indol-3-yl) ketones
from indoles and a-oxoaldehydes is described using an
inexpensive and commercially available catalyst such as ptoluenesulfonic
acid monohydrate. This protocol allows for the
first time the synthesis of 2,2-bis(indolyl)-1-alkylethanones by
employing aliphatic 2-oxoaldehydes, even as aqueous solutions.
The high-yielded obtained ketones have been shown as
useful starting materials for further synthetic transformations.