The Catellani reaction is known as a powerful strategy for the expeditious synthesis of highly substituted arenes and benzo‐fused rings, which are usually difficult to access through traditional ...cross‐coupling strategies. It utilizes the synergistic interplay of palladium and norbornene catalysis to facilitate sequential ortho C−H functionalization and ipso termination of aryl halides in a single operation. In classical Catellani‐type reactions, aryl halides are mainly used as the substrates, and a Pd0 catalyst is required to initiate the reaction. Nevertheless, recent advances showcase that Catellani‐type reactions can also be initiated by a PdII catalyst with different starting materials instead of aryl halides via different reaction mechanisms and under different conditions. This emerging concept of PdII/norbornene cooperative catalysis has significantly advanced Catellani‐type reactions, thus enabling future developments of this field. In this Minireview, PdII‐initiated Catellani‐type reactions and their application in the synthesis of bioactive molecules are summarized.
Cooperative solutions: Palladium(II)‐initiated norbornene (NBE)‐mediated cooperative catalysis has enabled significant developments of the Catellani reaction. These advances and their application in the synthesis of bioactive molecules are summarized in this Minireview.
The golden touch: Total synthesis of natural (−)‐englerin A from (R)‐citronellal has been achieved using a gold‐catalyzed cyclization as the key step (see scheme). No protecting‐group manipulations ...were required in the synthetic sequence.
Here, we report on a scalable route to the polyhydroxylated steroid ouabagenin with an unusual take on the age-old practice of steroid semisynthesis. The incorporation of both redox and ...stereochemical relays during the design of this synthesis resulted in efficient access to more than 500 milligrams of a key precursor toward ouabagenin—and ultimately ouabagenin itself—and the discovery of innovative methods for carbon-hydrogen (C-H) and carbon-carbon activation and carbon-oxygen bond homolysis. Given the medicinal relevance of the cardenolides in the treatment of congestive heart failure, a variety of ouabagenin analogs could potentially be generated from the key intermediate as a means of addressing the narrow therapeutic index of these molecules. This synthesis also showcases an approach to bypass the historically challenging problem of selective C-H oxidation of saturated carbon centers in a controlled fashion.
Heterocycles 2-pyridone and uracil are privileged pharmacophores. Diversity-oriented synthesis of their derivatives is in urgent need in medicinal chemistry. Herein, we report a palladium/norbornene ...cooperative catalysis enabled dual-functionalization of iodinated 2-pyridones and uracils. The success of this research depends on the use of two unique norbornene derivatives as the mediator. Readily available alkyl halides/tosylates and aryl bromides are utilized as ortho-alkylating and -arylating reagents, respectively. Widely accessible ipso-terminating reagents, including H/DCO
Na, boronic acid/ester, terminal alkene and alkyne are compatible with this protocol. Thus, a large number of valuable 2-pyridone derivatives, including deuterium/CD
-labeled 2-pyridones, bicyclic 2-pyridones, 2-pyridone-fenofibrate conjugate, axially chiral 2-pyridone (97% ee), as well as uracil and thymine derivatives, can be quickly prepared in a predictable manner (79 examples reported), which will be very useful in new drug discovery.
(Bioiso)steering in a new direction: A modular synthesis of reagents (e.g. sodium difluoroethylsulfinate) that can be used for the direct incorporation of difluoroalkyl groups onto heterocycles is ...reported. The scope and generality of the incorporation of difluoroalkyl groups is exemplified with the difluoroethyl group and a proof of principle is shown for a general synthesis of fluorinated heteroarylether bioisosteres.
The Catellani reaction is a powerful strategy that allows the expeditious synthesis of highly substituted arenes, which are not easily accessible through traditional transition‐metal‐catalyzed ...cross‐coupling reactions. This reaction utilizes the synergistic interplay of palladium and norbornene catalysis to facilitate sequential ortho‐C−H functionalization and ipso termination of aryl iodides in a single operation. Since pioneering work by the group of Catellani in 1997, and later by the group of Lautens, this chemistry has attracted considerable attention from the synthetic chemistry community. Dramatic progress has been made by a number of groups in the past two decades. In this Minireview, the alkylating reagents employed in this intriguing reaction and the corresponding applications in organic synthesis are summarized; thus complementing existing reviews to inspire future developments.
Changing conventions: The Catellani reaction, such as depicted, is a powerful strategy that allows the expeditious synthesis of highly substituted arenes, which are not easily accessible through traditional transition‐metal‐catalyzed cross‐coupling reactions (NBE=norbornene). This review highlights the alkylating reagents employed in these reactions and related applications in organic synthesis.
A convergent approach to assemble the fused BCDE tetracyclic framework of wortmannin is presented. This route features a very challenging Suzuki–Miyaura coupling to prepare the fully functionalized ...furan intermediate, a Negishi-type acylation to unite the two enantio-enriched fragments, and a subsequent hydrogen-atom-transfer-initiated 6-endo radical cyclization to install the central cyclohexadienone moiety, which establishes the C10 all-carbon quaternary stereocenter.
Reported is a novel palladium(II)‐initiated Catellani‐type reaction that utilizes widely accessible aryl boronic acids as the substrates instead of aryl halides, thereby greatly expanding the ...existing scope of this powerful transformation. This borono‐Catellani reaction was promoted by cooperative catalysis between Pd(OAc)2 and the inexpensive 5‐norbornene‐2‐carbonitrile. Practicality is the striking feature of the reaction: it is run open to air at ambient temperature and no phosphine ligand is needed. This mild, chemoselective, and scalable protocol is compatible with a large range of readily available functionalized aryl boronic acids and bromides, as well as terminating olefins (50 examples, 39–97 % yields). Moreover, the orthogonal reactivity between the borono‐Catellani and classical Catellani reaction was demonstrated. This work is expected to open new avenues for developing novel Catellani‐type reactions.
Put a B on it: A PdII‐initiated borono‐Catellani reaction using readily available aryl boronic acids as the substrates, instead of aryl halides, was developed. The reaction is promoted by Pd(OAc)2 and 5‐norbornene‐2‐carbonitrile, and is run open to air at ambient temperature without a phosphine ligand. This chemoselective protocol is compatible with a range of functionalized aryl boronic acids and bromides, as well as terminating olefins.
A practical C–H functionalization method for the methylation of heteroarenes is presented. Inspiration from Nature’s methylating agent, S-adenosylmethionine (SAM), allowed for the design and ...development of zinc bis(phenylsulfonylmethanesulfinate), or PSMS. The action of PSMS on a heteroarene generates a (phenylsulfonyl)methylated intermediate that can be easily separated from unreacted starting material. This intermediate can then be desulfonylated to the methylated product or elaborated to a deuteriomethylated product, and can divergently access medicinally important motifs. This mild, operationally simple protocol that can be conducted in open air at room temperature is compatible with sensitive functional groups for the late-stage functionalization of pharmacologically relevant substrates.
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