Metal-Free Cyclocarboamination of ortho-Formyl Phenylacetylenes with Secondary Amines: Access to 1,3-Diamino-1H-Indenes and 3-Amino-1-Indanones

This work first discloses a new strategy for amine activation to give reactive amine anion by in situ generated iminium cation-amine anion pair through decomposition of sterically hindered aminals. Utilizing this strategy, a highly regio- and chemoselective cyclocarboamination of ortho-formyl phenylacetylenes with secondary amines has been realized under metal-free mild reaction conditions. The cyclocarboamination with notably tunable product profiles depends on the separation and purification procedure, a diverse range of 1, 3-diamino-1H-indenes (essentially reactive enamines) and 3-amino-1-indanones were obtained, respectively. Moreover, using iodine as an electrophile to couple with various ortho-formyl phenylacetylenes and secondary amines, a series of 3-amino-2-iodo-1-indanones were efficiently achieved with four bonds (C=O, C−C, C−N and C−I) formation in an one-pot three-component reaction. These results demonstrated an unprecedented methodology for the construction of highly functionalized 1H-indene and 1-indanone compounds. (Figure presented.).