Pick your Pd partners: A number of catalytic systems have been developed for palladium-catalyzed CH activation/CC bond formation. Recent studies concerning the palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle are discussed (see scheme), and the versatility and practicality of this new mode of catalysis are presented. Unaddressed questions and the potential for development in the field are also addressed.

In the past decade, palladium-catalyzed CH activation/CC bond-forming reactions have emerged as promising new catalytic transformations; however, development in this field is still at an early stage compared to the state of the art in cross-coupling reactions using aryl and alkyl halides. This Review begins with a brief introduction of four extensively investigated modes of catalysis for forming CC bonds from CH bonds: PdII/Pd0, PdII/PdIV, Pd0/PdII/PdIV, and Pd0/PdII catalysis. A more detailed discussion is then directed towards the recent development of palladium(II)-catalyzed coupling of CH bonds with organometallic reagents through a PdII/Pd0 catalytic cycle. Despite the progress made to date, improving the versatility and practicality of this new reaction remains a tremendous challenge.

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Palladium(II)-catalyzed C-H activation/C-C cross-coupling reactions: versatility and practicality.

The area of transition-metal-catalyzed direct arylation through cleavage of CH bonds has undergone rapid development in recent years, and is becoming an increasingly viable alternative to traditional cross-coupling reactions with organometallic reagents In particular, palladium and ruthenium catalysts have been described that enable the direct arylation of (hetero)arenes with challenging coupling partners—including electrophilic aryl chlorides and tosylates as well as simple arenes in cross-dehydrogenative arylations Furthermore, less expensive copper, iron, and nickel complexes were recently shown to be effective for economically attractive direct arylations

Transition-metal-catalyzed direct arylation of (hetero)arenes by C-H bond cleavage.

In 2010, Richard Heck, Ei-ichi Negishi, and Akira Suzuki joined the prestigious circle of Nobel Laureate chemists for their roles in discovering and developing highly practical methodologies for C-C bond construction. From their original contributions in the early 1970s the landscape of the strategies and methods of organic synthesis irreversibly changed for the modern chemist, both in academia and in industry. In this Review, we attempt to trace the historical origin of these powerful reactions, and outline the developments from the seminal discoveries leading to their eminent position as appreciated and applied today.

Palladium-Catalyzed Cross-Coupling: A Historical Contextual Perspective to the 2010 Nobel Prize

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Advances in transition metal (Pd, Ni, Fe)-catalyzed cross-coupling reactions using alkyl-organometallics as reaction partners.

This Review summarizes the advancements in Pd-catalyzed C(sp3)–H activation via various redox manifolds, including Pd(0)/Pd(II), Pd(II)/Pd(IV), and Pd(II)/Pd(0). While few examples have been reported in the activation of alkane C–H bonds, many C(sp3)–H activation/C–C and C–heteroatom bond forming reactions have been developed by the use of directing group strategies to control regioselectivity and build structural patterns for synthetic chemistry. A number of mono- and bidentate ligands have also proven to be effective for accelerating C(sp3)–H activation directed by weakly coordinating auxiliaries, which provides great opportunities to control reactivity and selectivity (including enantioselectivity) in Pd-catalyzed C–H functionalization reactions.

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Palladium-Catalyzed Transformations of Alkyl C-H Bonds.

In the panoply of modern synthetic methods for forming carbon−carbon and carbon−heteroatom bonds, the transition metal-catalyzed cross-coupling of organometallic nucleophiles with organic electrophiles enjoys a preeminent status. The preparative utility of these reactions is, in large measure, a consequence of the wide variety of organometallic donors that have been conscripted into service. The most common of these reagents are organic derivatives of tin, boron, and zinc, which each possess unique advantages and shortcomings. Because of their low cost, low toxicity, and high chemical stability, organosilanes have emerged as viable alternatives to the conventional reagents in recent years. However, unlike the tin- and zinc-based reactions, which require no activation, or the boron-based reactions, which require only heating with mild bases, silicon-based cross-coupling reactions often require heating in the presence of a fluoride source; this has significantly hampered the widespread acceptance of organos...

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Palladium-catalyzed cross-coupling reactions of organosilanols and their salts: practical alternatives to boron- and tin-based methods.

Total synthesis of papulacandin D.

Kinetic, spectroscopic, crystallographic, and computational studies probing a Pd-catalyzed C–H arylation reaction reveal that mono-oxidation of the bis-phosphine ligand is critical for the formation of the active catalyst. The bis-phosphine mono-oxide is shown to be a hemilabile, bidentate ligand for palladium. Isolation of the oxidative addition adduct, with structural elucidation by X-ray analysis, showed that the mono-oxide was catalytically competent, giving the same reaction rate in the productive reaction as the Pd(II)/xantphos precursor. A dual role for the carboxylate base in both catalyst activation and reaction turnover was demonstrated, along with the inhibiting effect of excess phosphine ligand. The generality of the role of phosphine mono-oxide complexes in Pd-catalyzed coupling processes is discussed.

Mono-Oxidation of Bidentate Bis-phosphines in Catalyst Activation: Kinetic and Mechanistic Studies of a Pd/Xantphos-Catalyzed C-H Functionalization.

A total synthesis of (+)-papulacandin D which shows an antifungal activity is reported The molecule is one of the members of C-arylglycoside isolated from Papularia spherosperma The synthetic strategy bifurcates the molecule into two nearly equal subunits, the aryl glycoside and 18-carbon fatty acid side chain The key strategic transformations are (1) the palladium catalyzed, organosilanolate-based cross-coupling of a protected glucal silanol and (2) a catalytic enantioselective allylation of a dienal using allyltrichlorosilane This highly convergent synthesis was accomplished in 31 steps overall from commercial starting materials

https://www.jstage.jst.go.jp/article/yukigoseikyokaishi1943/66/6/66_6_616/_pdf

Total Synthesis of Papulacandin D

http://ccc.chem.pitt.edu/wipf/Courses//2320_07_files/JournalClub/Papulacandin.pdf

Christopher S. Regens

Papers

Palladium-catalyzed cross-coupling reactions of organosilanols and their salts: practical alternatives to boron- and tin-based methods.

Total synthesis of papulacandin D.

Mono-Oxidation of Bidentate Bis-phosphines in Catalyst Activation: Kinetic and Mechanistic Studies of a Pd/Xantphos-Catalyzed C-H Functionalization.

Total Synthesis of Papulacandin D

Total Synthesis of (+)-Papulacandin D