A π-conjugated covalent organic framework enables interlocked nickel/photoredox catalysis for light-harvesting cross-coupling reactions.

Covalent organic frameworks (COFs) are an outstanding platform for heterogeneous photocatalysis. Herein, we synthesized a pyrene-based two-dimensional C[double bond, length as m-dash]C linked π-conjugated COF via Knoevenagel condensation and anchored Ni(ii)-centers through bipyridine moieties. Instead of traditional dual metallaphotoredox catalysis, the mono-metal decorated Ni@Bpy-sp2c-COF interlocked the catalysis mediated by light and the transition metal. Under light irradiation, enhanced energy and electron transfer in the COF backbone, as delineated by the photoluminescence, electrochemical, and control experiments, expedited the excitation of Ni centers to efficiently catalyze diverse photocatalytic C-X (X = B, C, N, O, P, S) cross-coupling reactions with efficiencies orders of magnitude higher than the homogeneous controls. The COF catalyst tolerated a diverse range of coupling partners with various steric and electronic properties, delivering the products with up to 99% yields. Some reactions were performed on a gram scale and were applied to diversify pharmaceuticals and complex molecules to demonstrate the synthetic utility.

Dual Metalation in a Two-Dimensional Covalent Organic Framework for Photocatalytic C-N Cross-Coupling Reactions.

Covalent organic frameworks (COFs) are promising hosts in heterogeneous catalysis. Herein, we report a dual metalation strategy in a single two-dimensional-COF TpBpy for performing a variety of C-N cross-coupling reactions. [Ir(ppy)2(CH3CN)2]PF6 [ppy = 2-phenylpyridine], containing two labile CH3CN groups, and NiCl2 are used as iridium and nickel-metal precursors, respectively, for postsynthetic decoration of the TpBpy COF. Moving from the traditional approach, we focus on the COF-backbone host for visible-light-mediated nickel-catalyzed C-N coupling reactions. The controlled metalation and recyclability without deactivation of both catalytic centers are unique with respect to previously reported coupling strategies. We performed various photoluminescence, electrochemical, kinetic, and Hammett correlation studies to understand the salient features of the catalyst and reaction mechanism. Furthermore, theoretical calculations delineated the feasibility of electron transfer from the Ir center to the Ni center inside the confined pore of the TpBpy COF. The dual metal anchoring within the COF backbone prevented nickel-black formation. The developed protocol enables selective and reproducible coupling of a diverse range of amines (aryl, heteroaryl, and alkyl), carbamides, and sulfonamides with electron-rich, neutral, and poor (hetero) aryl iodides up to 94% isolated yield. The reaction can also be performed on a gram scale. Furthermore, to establish the practical implementation of this approach, we have applied the synthetic strategy for the late-stage diversification of the derivatives of ibuprofen, naproxen, gemfibrozil, helional, and amino acids. The methodology could also be applied to synthesize pharmacophore N,5-diphenyloxazol-2-amine and Food and Drug Administration-approved drugs, including flufenamic acid, flibanserin, and tripelennamine.

Manganese complex-catalysed α-alkylation of ketones with secondary alcohols enables the synthesis of ß-branched carbonyl compounds.

Herein, ß-branched carbonyl compounds were synthesised via the α-alkylation of ketones with secondary alcohols under "borrowing hydrogen" catalysis. A wide range of secondary alcohols, including various cyclic, acyclic, symmetrical, and unsymmetrical alcohols, have been successfully applied under the developed reaction conditions. A manganese(i) complex bearing a phosphine-free multifunctional ligand catalysed the reaction and produced water as the sole byproduct.