Iron-Catalyzed Functionalization of 3-Benzylideneindoline Through Tandem Csp2-Csp3 Bond Formation/Isomerization with π-Activated Alcohols

A new synthetic protocol was developed for the selective synthesis of diverse 3-substituted indoles through tandem carbon-carbon bond formation and isomerization of 3-benzylidene-1-tosylindoline by direct use of alcohols as alkylating agents in the presence of catalytic FeCl3. This method is applicable to a wide range of substrates containing varieties of functional groups. Direct use of alcohols, such as benzylic, allylic, and propargylic alcohols, as electrophiles and the use of non-toxic iron catalyst makes this strategy attractive and environmentally benign. A plausible mechanism has also been proposed for this tandem reaction.