C−H functionalization of aliphatic carboxylic acids without attaching exogenous auxiliary has been so far limited at the proximal β‐position. In this work, we demonstrate a ligand enabled palladium catalyzed first regioselective distal γ‐C(sp3)−H functionalization of aliphatic carboxylic acids without incorporating an exogenous directing group. Aryl iodides containing versatile functional groups including complex organic molecules are well tolerated with good to excellent yields during the γ‐C(sp3)−H arylation reaction. Interestingly, weak coordination of carboxylate group can be further extended for sequential hetero di‐arylation. Application of the protocol has been showcased by synthesizing substituted α‐tetralone. Mechanistic investigations have been carried out to shed light on the reaction pathway.
The Fujiwara-Moritani reaction has had a profound contribution in the emergence of contemporary C-H activation protocols. Despite the applicability of the traditional approach in different elds, the associated reactivity and regioselectivity issues had rendered it redundant. The revival of this exemplary reaction requires the development of a mechanistic paradigm that would have simultaneous control on both the reactivity and regioselectivity. Often high thermal energy required to promote ole nation leads to multiple site functionalization. To this aim we established a photoredoxcatalytic system constituting a merger of palladium/organo-photocatalyst that forges oxidative ole nation in an explicit regioselective fashion of diverse arenes and heteroarenes. Visible light plays a signi cant role in executing 'regio-resolved' Fuijiwara-Moritani reaction without the requirement of silver salts and thermal energy. The catalytic system is also amenable towards proximal and distal ole nation aided by respective directing groups (DGs), which entails the versatility of the protocol in engaging the entire spectrum of C(sp2)-H ole nation.Furthermore, streamlining the synthesis of natural products, chiral molecules, drugs and diversi cation through late-stage functionalizations underscore the importance of this sustainable protocol. The photoinduced attainment of this regioselective transformation is mechanistically established through control reactions, kinetic studies and theoretical calculations.
We thank the Fonds der Chemischen Industrie (Liebig fellowship for D.M.), the German‐American Fulbright Commission (Fulbright‐Cottrell Award for D.M.) as well as the Bavarian Equal Opportunities Sponsorship – Realization of Equal Opportunities for Women in Research and Teaching (fellowship for A.G.) for financial support. We thank the RRZ Erlangen for computational resources.
Directed C−H functionalization has been realized as a complementary tool to the traditional approaches for a straightforward access of non‐proteinogenic amino acids; albeit such a process is restricted mostly up to the γ‐position. In the present work, we demonstrate the diverse (hetero)arylation of amino acids and analogous aliphatic amines selectively at the remote δ‐position by tuning the reactivity controlled by ligands. An organopalladium δ‐C(sp3)−H activated intermediate has been isolated and crystallographically characterized. Mechanistic investigations carried out experimentally in conjunction with computational studies shed light on the difference in the mechanistic picture depending on the substrate structure.
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