title: Electronic Nature of Ketone Directing Group as a Key To Control C-2 vs C-4 Alkenylation of Indoles.
abstract: A novel mode of achieving site selectivity between C-2 and C-4 positions in the indole framework by altering the property of the ketone directing group is disclosed. Methyl ketone, as directing group, furnishes exclusively C-2 alkenylated product, whereas trifluoromethyl ketone changes the selectivity to C-4, indicating that the electronic nature of the directing group controls the unusual choice between a 5-membered and a 6-membered metallacycle. The screening of other carbonyl-derived directing groups reveals that strong and weak directing groups exhibit opposite selectivity. Experimental controls and deuteration experiments lend support to the proposed mechanism.
authors.affiliation: Department of Organic Chemistry, Indian Institute of Science , Bangalore 560 012, Karnataka, India.
authors.forename: Veeranjaneyulu
authors.initials: V
authors.lastname: Lanke
authors.affiliation: Department of Organic Chemistry, Indian Institute of Science , Bangalore 560 012, Karnataka, India.
authors.forename: Kiran R
authors.initials: KR
authors.lastname: Bettadapur
authors.affiliation: Department of Organic Chemistry, Indian Institute of Science , Bangalore 560 012, Karnataka, India.
authors.forename: Kandikere Ramaiah
authors.initials: KR
authors.lastname: Prabhu