Synthesis of 2,3-polymethylene-3H-indoles from 2,3-polymethylene-1H-indolylmagnesium halides : oxidative rearrangement to spiro[cycloalkane-1,2'-indolin]-3'-one

Reaction of 2,3-polymethylene-1H-indolylmagnesium iodides with methyl iodide gives the C-methyl derivative and the spiro [cycloalkane-1,2'-indolin]-3'-one; the selectivity and optimization of the reaction has been analysed and a mechanism for the formation of the oxidation product is proposed