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A palladium-catalyzed [4 + 3] annulation of 2-bromobiphenyls and epoxides for the construction of dihydrodibenzo[b,d]oxepines is reported.

Herein, we report a modular and convergent strategy for the assembly of atropisomeric o-terphenyls with 1,2-diaxes via palladium/chiral norbornene cooperative catalysis and axial-to-axial diastereoinduction. Readily available aryl iodides, 2,6-substituted aryl bromides, and potassium aryl trifluoroborates are used as the building blocks, laying the foundation for diversity-oriented synthesis of these scaffolds (46 examples). Other features include the unique axial-to-axial diastereoinduction mode, construction of two axes in a single operation, and step economy. DFT calculations are performed to rationalize the axial-to-axial diastereoinduction process. Synthetic utilities of this method in preparation of atropisomeric oligophenyls, chiral catalysts, and ligands are demonstrated.

Reported here is a concise total synthesis of (-)-berkelic acid in eight linear steps. This synthesis features a Catellani reaction/oxa-Michael cascade for the construction of the isochroman scaffold, a one-pot deprotection/spiroacetalization operation for the formation of the tetracyclic core structure, and a late-stage Ni-catalyzed reductive coupling for the introduction of the lateral chain. Notably, four stereocenters are established from a single existing chiral center with excellent stereocontrol during the deprotection/spiroacetalization process. Stereocontrol of the intriguing deprotection/spiroacetalization process is supported by DFT calculations.

Reported is a cooperative catalytic system consisting of a complex of Pd with dicyclohexyl(2′,4′,6′-triisopropylbiphenyl-2-yl)phosphine (XPhos) and the potassium salt of 5-norbornene-2-carboxylic acid that permits the use of epoxides as dual-functionalized alkylating reagents in Catellani-type reactions for the assembly of heterocycles. Salient features of this research include readily available substrates, use of the potassium salt of 5-norbornene-2-carboxylic acid as a catalytic mediator as well as a base, and excellent regioselectivity for the cleavage of epoxides. This mild, chemoselective, scalable, atom- and step-economic protocol offers a straightforward approach for the assembly of isochroman and 2,3-dihydrobenzofuran scaffolds.

Herein we report an asymmetric two-component vinylogous Catellani reaction for the construction of C-N axial chirality through a palladium/chiral norbornene cooperative catalysis and an axial-to-axial chirality transfer process. Various partially aromatic iodinated 2-pyridones, quinolones, coumarin and uracil substrates react with 2,6-disubstituted aryl bromides with a tethered amide group, to afford a wide variety of polycyclic C-N atropisomers (39 examples, up to 97% ee ). The obtained C-N axial chirality is originated from the preformed transient C-C axial chirality with high fidelity. The synthetic utility of this chemistry is demonstrated by facile preparation of complex quinoline and pyridine based C-N atropisomers through a N -deprotection and aromatization sequence. In addition, a remote axial-to-central diastereoinduction process dictated by C-N axial chirality is observed with excellent diastereocontrol. This research opens a new avenue for asymmetric synthesis.

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/DCO2Na, boronic acid/ester, terminal alkene and alkyne are compatible with this protocol. Thus, a large number of valuable 2-pyridone derivatives, including deuterium/CD3-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., Diversity-oriented synthesis of 2-pyridone and uracil derivatives is in urgent need in medicinal chemistry as they are useful pharmacophores. Here the authors show that palladium/norbornene cooperative catalysis enabled dual-functionalization of iodinated 2- pyridones and uracils.

Herein, we report a modular and convergent strategy for the assembly of atropisomeric

Reported is a modular strategy for the preparation of the unique benzofused dioxabicycle scaffolds involving a Catellani reaction of aryl iodides, epoxides, and terminal alkynes and an oxa-cyclizat...

Silver-catalyzed tandem cyclization–elimination reactions of conjugated ene-yne-ketones in PhI(OAc)2/triethylamine system lead to the formation of 2-alkenylfurans. 2-Furylsilver carbene and phenyli...

The regioselective addition mechanism of the Ti(IV) enolates derived from α-diazo-β-keto carbonyl compounds and α-diazo-β-keto phosphonates to conjugated enones has been studied on the basis of a hypothetical bridging chloride-controlled theory, by density functional theory (DFT), and experimentally. The DFT results indicate that, for the Ti(IV) enolate 3 derived from α-diazo-β-keto carbonyl compounds, the free energy of the bridging chloride-controlled 1,2-addition transition state is 2.4 kcal/mol higher than that of 1,4-addition, and the calculated enthalpies of 1,2-addition is 4.36 kcal/mol more than that of 1,4-addition. For the Ti(IV) enolate 4 derived from α-diazo-β-keto phosphonates, in contrary, the free energy of the bridging chloride-controlled 1,2-addition transition state is 1.1 kcal/mol lower than that of 1,4-addition, and the calculated enthalpy of 1,2-addition is 3.46 kcal/mol less than that of 1,4-addition. Our findings demonstrate that the nucleophilic addition of these Ti(IV) enolates to conjugated enones was carried out not only kinetically but also irreversibly for the first time.

We report a cooperative catalytic system comprising a PdII complex, XPhos, and the potassium salt of 5-norbornene-2-carboxylic acid that enables the use of epoxides as alkylating reagents in the Catellani reaction, thereby expanding the existing paradigm of this powerful transformation. The potassium salt of inexpensive 5-norbornene-2-carboxylic acid acts as both mediator and base in the process. This mild, chemoselective, scalable, and atom-economical protocol is compatible with a wide variety of readily available functionalized aryl iodides and epoxides, as well as terminating olefins. The resulting products undergo facile oxa-Michael addition to furnish ubiquitous isochroman scaffolds.

A cooperative catalytic system comprising a Pd/XPhos complex and a potassium salt of 5-norbornene-2-carboxylic acid to promote the annulation between aryl iodides and epoxides was developed, thereby providing highly convergent access to valuable 2,3-dihydrobenzofuran (DHBF) scaffolds. The unique potassium salt of the inexpensive 5-norbornene-2-carboxylic acid serves as a highly efficient catalytic mediator (10 mol%), which leads to fewer side reactions. The salient features of the reaction include its broad substrate scope (with respect to both aryl iodides and epoxides), its high atom economy and good chemo-selectivity. Furthermore, no extra base is needed for the process.

Silver-catalyzed tandem cyclization-elimination reactions of conjugated ene-yne-ketones in PhI(OAc)

A new synthetic method for α-alkynyl-α,β-unsaturated esters is presented herein. The method is based on a copper(I)-catalyzed three-component reaction of a terminal alkyne, diazoesters and aldehydes. The reaction is featured by mild conditions, high yields and excellent stereoselectivity. Cu(I) carbene migratory insertion is proposed as the key step in the transformation.

Through the Cu(I)-catalyzed coupling of diazophosphonates with terminal alkynes, an efficient method for the synthesis of allenylphosphonates has been developed. Simple and inexpensive CuI is used as the catalyst and the reaction is conducted under mild conditions.

A highly efficient method for the synthesis of tri-aryl-substituted allenes has been developed through Cu(I)-catalyzed coupling of diaryldiazomethanes with terminal alkynes. The reaction is under mild conditions and uses simple and inexpensive CuI as the catalyst. Mechanistically, the reaction follows a pathway involving Cu(I) carbene migratory insertion.

A transition-metal-free difluoromethylenation of diazo compounds that proceeds under mild conditions has been developed and is based on the use of TMSCF2 Br as the difluoromethylene source and tetrabutylammonium bromide (TBAB) as the promoter. The chemoselective formal carbene dimerization reaction is achieved owing to the electronic properties and the relative stability of the difluorocarbene intermediate.

Through the Cu(I)-catalyzed coupling of diazophosphonates with terminal alkynes, an efficient method for the synthesis of allenylphosphonates has been developed. Simple and inexpensive CuI is used as the catalyst and the reaction is conducted under mild conditions.

The title compounds are chemoselectively obtained by transition-metal-free difluoromethylenation of various diazo compounds under mild reaction conditions.

A highly efficient method for the synthesis of tri-aryl-substituted allenes has been developed through Cu(I)-catalyzed coupling of diaryldiazomethanes with terminal alkynes. The reaction is under mild conditions and uses simple and inexpensive CuI as the catalyst. Mechanistically, the reaction follows a pathway involving Cu(I) carbene migratory insertion.

A Cu-catalyzed three-component cross-coupling reaction of terminal alkyne, α-diazo ester, and alkyl halide has been developed. This transformation involves sequent migratory insertion of copper-carbene and nucleophilic substitution, in which a C(sp)–C(sp3) bond and a C(sp3)–C(sp3) bond are formed successively on a carbenic center. Michael addition acceptors can also be employed instead of alkyl halides that enable Michael addition to be an alternative way to build C(sp3)–C(sp3) bond. This transformation represents a highly efficient method for the construction of all-carbon quaternary centers.

A Cu-catalyzed three-component cross-coupling reaction of terminal alkyne, α-diazo ester, and alkyl halide has been developed. This transformation involves sequent migratory insertion of copper-carbene and nucleophilic substitution, in which a C(sp)-C(sp(3)) bond and a C(sp(3))-C(sp(3)) bond are formed successively on a carbenic center. Michael addition acceptors can also be employed instead of alkyl halides that enable Michael addition to be an alternative way to build C(sp(3))-C(sp(3)) bond. This transformation represents a highly efficient method for the construction of all-carbon quaternary centers.