Regiodivergent CDC reactions of aromatic aldehydes with unactivated arenes controlled by transient directing strategy

The regiodivergent catalytic dehydrogenative cross-coupling reactions at both sp 2 and sp 3 hybridized carbons of aromatic compounds are particularly challenging. Herein, we report the finding of transient directing group controlled regiodivergent C(sp 3 )-C(sp 2 ) and C(sp 2 )-C(sp 2 ) cross-coupling in the o -methyl benzaldehyde frameworks. Catalyzed by palladium, using K 2 S 2 O 8 or [F + ] reagents as by-standing oxidants and unactivated arenes as substrates/solvents, various benzyl benzaldehydes or phenyl benzaldehydes were prepared. A mechanism study indicated that the regiospecificity is dominated by the [5,6]-fused palladacycle or [6,5]-fused palladacycle intermediates, which are generated from Pd-chelation with specified transient directing groups and further C-H activations. It was found for the first time that transient directing group controlled regiodivergent CDC reactions at both sp 2 and sp 3 hybridized carbons of aromatic compounds with palladium catalyst.