Benzylic C–H addition of aromatic amines to alkenes using a scandium catalyst

Abstract

An efficient and selective benzylic C(sp3)-H addition of o-CH3-substituted tertiary aromatic amine to alkene has been achieved using an anilido-oxazoline ligand supported scandium catalyst, which provides an atom-economic method for...

Scandium-Catalyzed Benzylic C(sp3)–H Alkenylation of Tertiary Anilines with Alkynes

“…In particular, half-sandwich rare-earth complexes showed unique activities and selectivities in catalytic C–H additions to a variety of alkenes and alkynes . In our prior work, we showed that the cationic rare-earth-metal complexes supported by unsymmetric β-diketiminato-type ligands enabled the versatile C–H functionalization of anilines, such as para -C­(sp 2 )–H alkylation with alkenes, C­(sp 2 )–H/N–H annulation with allenes and dienes, α-C­(sp 3 )–H alkylation with alkenes, and benzylic C­(sp 3 )–H alkylation with alkenes . These reactions demonstrated promising results, owing to the strong nitrogen affinity of rare-earth-metal ions.…”

“…12 In our prior work, we showed that the cationic rare-earth-metal complexes supported by unsymmetric β-diketiminato-type ligands enabled the versatile C−H functionalization of anilines, such as para-C(sp 2 )−H alkylation with alkenes, 13 C(sp 2 )−H/N−H annulation with allenes and dienes, 14 α-C(sp 3 )−H alkylation with alkenes, 15 and benzylic C(sp 3 )−H alkylation with alkenes. 16 These reactions demonstrated promising results, owing to the strong nitrogen affinity of rare-earth-metal ions. Further study herein disclosed that a scandium complex based on a simple β-diketiminato ligand could also be applied for the benzylic C(sp 3 )−H addition of tertiary ortho-methyl anilines to a variety of internal alkynes with high chemo-and stereoselectivity (Scheme 1c).…”

Transition-metal-catalyzed C–H bond alkylation using olefins: recent advances and mechanistic aspects

“…Recently, the Xu group reported Sc-catalyzed ortho -benzylic C–H alkylation of tertiary anilines 170a using various alkenes 170b , which rendered moderate to good yields (Scheme 170). 269 The easily available anilido-oxazoline ligand bound Sc-complex enabled the reaction with high atom economy, a good substrate scope, high functional group tolerance and substrate-dependent regioselectivity. The reaction proceeded via the generation of cationic monoalkyl Sc-species 170h with the help of [PhNHMe 2 ][B(C 6 F 5 ) 4 ].…”

Recent progress in rare-earth metal-catalyzed sp2 and sp3 C–H functionalization to construct C–C and C–heteroelement bonds

“…Recognizing these aspects, recently Xu and co-workers demonstrated the selective benzylic sp 3 C–H addition of ortho -methyl N , N -dimethylaniline scaffolds with allylarenes and unactivated aliphatic alkenes in the presence of a non-metallocene bulky β-diketiminato-type anilido-oxazoline ligand-supported Sc-dialkyl complex as catalyst 12 -Sc in combination with catalytic [PhNHMe 2 ][B(C 6 F 5 ) 4 ] as an activator (Scheme 16A). 97 The Y analogue of 12 -Sc was found to be ineffective for the transformation, which is most likely because the ligand framework could not stabilize the cationic active species of the Y centre. Perhaps this report represents the first example of achieving the sp 3 C–H alkylation of the benzylic methyl group of anilines with alkenes under Sc catalysis.…”