Evolving Oxeto-Indolinic Polycycles from Indoles by Means of a Visible-Light [2+2] Heterocycloaddition Dearomatization Process

A large variety of highly functionalized N-containing polycycles (35 examples) are synthetized from simple indoles and aromatic ketones through a mild visible-light-driven [2+2]-heterocycloaddition process. Tetrahydrooxeto[2,3b]indole scaffolds, with up to three contiguous all-substituted stereo-centers are generated in high yield (up to >98%) and excellent site- regio- and diastereocontrol (>20:1). The use of visible light (405 or 465 nm) ensures enhanced performances by switching off undesired photodimerization reactions. Mechanistic investigations revealed that the operative reaction mechanism is dependent by the nature of the used ketone-substrate.