Synthesis of γ-Lactams via Pd(II)-Catalyzed C(sp3)-H Olefination Using a Self-Cleaving Polyfluoroethylsulfinyl Directing Group

Synthesis of lactones and lactams via C(sp3)-H bond functionalization

The field of directing group-assisted, transition-metal-catalyzed functionalization has undergone a significant transformation, evolving from the use of auxiliary group attachment for the exploitation of native functional groups in novel organic reactions. In particular, coordination-assisted C(sp3)-H bond functionalization has revolutionized synthetic planning to build molecular complexity. Recently, the use of native directing groups in transition-metal-catalyzed reactions has allowed a step-economic process for increased access to biologically important lactones and lactams. Accordingly, lactones and lactams are unavoidable structural motifs with widespread presence in many biological and pharmaceutical arenas, encouraging researchers to access and modify their structures for improved biological properties. In this review, we showcase the diverse aspects of transition metal catalysis, biocatalysis, and photocatalytic C(sp3)-H bond functionalization to access lactones and lactams assisted by carboxylic acid and amines/amides with auxiliary or transient directing groups or unique ligands. This article also emphasizes the role of specially designed complexes, artificial metalloenzymes, and biocatalysts in assembling lactones and lactams. Besides, three-component reactions involving CO as a C1 synthon play a vital role in developing these heterocycles. Importantly, the crucial role of ligands in determining regioselectivity and enhancing enantioselectivity is discussed thoroughly. For better clarity, this review is divided into twelve sections based on the catalysts involved, with subsections categorized by the type of bond activation or formation. Overall, this review aims to inspire the growth of C(sp3)-H bond functionalization, leading to the integration of lactams and lactones in organics.

Research on transition metals for the multicomponent synthesis of benzo-fused γ-lactams

Benzo-fused γ-lactams are fundamental in medicinal chemistry, acting as essential elements for various therapeutic agents due to their structural adaptability and capability to enhance biological activity. In their synthesis, transition metals play a pivotal role as catalysts, offering more efficient alternatives to traditional methods by facilitating C-N bond formation through mechanisms like intramolecular coupling. Recent advances have especially spotlighted transition-metal-catalyzed C-H amination reactions for directly converting C(sp2)-H to C(sp2)-N bonds, streamlining the creation of these compounds. Furthermore, biocatalytic approaches have emerged, providing asymmetric synthesis of lactams with high yield and enantioselectivity. This review examined the transition metal-catalyzed synthesis techniques for producing benzo-fused γ-lactams, marking a significant leap in organic synthesis by proposing more effective, selective, and greener production methods. It serves as a valuable resource for researchers in the fields of transition metal catalysts and those engaged in synthesizing these lactams.

Complementary strategies for synthesis of sulfinamides from sulfur-based feedstock

We describe a straightforward one-pot reductive protocol for the synthesis of sulfinamides from sulfonyl chlorides. This method enables the preparation of sulfinamides with a broad range of functional groups. Furthermore, we have expanded a known oxidative pathway to sulfinamides starting from thiols. These methods together provide a general strategy for the synthesis of sulfinamides from common sulfur-based feedstock that is available with large structural and functional group diversity.

Diastereoselective palladium-catalyzed functionalization of prochiral C(sp3)-H bonds of aliphatic and alicyclic compounds

We highlight the reported developments of the palladium-catalyzed C-H activation and functionalization of the inactive/unreactive prochiral C(sp³)-H bonds of aliphatic and alicyclic compounds. There exist numerous classical methods for generating contiguous stereogenic centers in a compound with a high degree of stereocontrol. Along similar lines, the Pd(II)-catalyzed, directing group-aided functionalization of inactive prochiral/diastereotopic C(sp³)-H bonds have been exploited to accomplish the stereoselective construction of stereo-arrays in organic compounds. We present a concise discussion on how specific strategies consisting of Pd(II)-catalyzed, directing group-aided C(sp³)-H functionalization have been utilized to generate two or more stereogenic centers in aliphatic and alicyclic compounds.

Trans-selective cyclizations of alpha-bromocarboxamides and E/Z-mixed internal olefins catalyzed by a Fe salt

Herein, we describe a protocol for trans-selective cyclizations of α-bromocarboxamides and E/Z-mixed internal olefins catalyzed by a Fe salt.

A Mechanism Study for Self-Cleaving Chlorotetrafluoroethylsulfinyl (-SOCF2CF2Cl)-Directed Pd(II)-Catalyzed C-H Activation

A mechanism study for Pd(II)-catalyzed C(sp³)-H activation using a self-cleaving chlorotetrafluoroethylsulfinyl (-SOCF₂CF₂Cl) auxiliary as a directing group is reported. Mechanistic studies reveal that (1) the auxiliary group is crucial for C(sp³)-H activation, (2) the reaction undergoes a C(sp³)-H olefination-Michael addition-removal of the auxiliary sequence, (3) the removal of the auxiliary (SOR_f) is most likely the alcoholic solvolysis of the -SOCF₂CF₂Cl group on the N-tri-substituted sulfonamides, and (4) the C(sp³)-H cleavage is involved in the rate-determining step.

Gold-catalyzed oxidative cyclization of amide-alkynes: access to functionalized γ-lactams

An efficient gold-catalyzed oxidative cyclization of amide-alkynes is developed. A series of functionalized γ-lactams are easily accessed by employing this strategy. The tandem reaction proceeds through alkyne oxidation, carbene/alkyne metathesis, and donor/donor carbene oxidation.