Selective arylation/annulation cascade reactions of 2-alkynylanilines with diaryliodonium salts

An efficient Cu catalyzed selective arylation/annulation cascade reaction of 2-alkynylanilines with diaryliodonium salts was developed.This reaction was selective to N-arylation instead of C-arylation,which provides a simple synthetic method for N-aryl indoles.

Rhodium(Ⅲ)-catalyzed selective access to isoindolinones via formal [4+1] annulation of arylamides and propargyl alcohols

A mild and efficient oxidative synthesis of isoindolinones has been realized by Rh(III)‐catalyzed C?H activation of benzamides and[4+1]coupling with propargyl alcohols.This coupling system proceeds with broad substrate scope and mild conditions and provides a new approach to access the useful skeleton ofγ‐lactams with a stereogenic center.

Visible Light-Induced[3+2]Annulation Reaction of Alkenes with Vinyl Azides:Direct Synthesis of Functionalized Pyrroles

A photocatalytic[3+2]annulation of alkenes with vinyl azides was developed under irradiation by visible light in the presence of organic dye photocatalysts.Broad substrate scope and high functional group tolerance were demonstrated by more than 50 examples.The reaction provides a novel and efficient method for the synthesis of polyfunctionalized pyrroles under very mild metal-free conditions without other additives.

Metal-Free Photocatalytic[4+2]Annulation of Acrylamides with 2-Benzyl-2-bromocarbonyls to Assemble Tetralin-1-carboxamides

Tetralin-1-carboxamides are frequently incorporated in myriad medicinally important molecules.However,their existing synthetic routes not only suffer from some drawbacks such as tedious procedures,harsh reaction conditions,narrow substrate scope,low yields,and environmental problems,but are also based upon the elaboration of uneasily available non-linear tetralin derivatives.Herein,we describe a metal-and additive-free visible light-induced[4+2]annulation of two simple linear starting materials,namely acrylamides and 2-benzyl-2-bromocarbonyls,through a cascade C(sp^(3))-Br/C(sp^(2))-H bond cleavage,double C-C bond formation,and aromatization sequence.The developed protocol provides a convenient,efficient,and green approach to a variety of tetralin-1-carboxamide derivatives with good functional group compatibility.Importantly,the resulting products could also undergo the Licl-mediated mono-decarboxylative cyclization process to further furnish the architecturally novel bridged polycyclic imides with excellentcis-diastereoselectivities.

An Assembly of Pyrano[3,2-b]indol-2-ones via NHC-Catalyzed[3+3]Annulation of Indolin-3-ones with Ynals

We report herein an unprecedented N-heterocyclic carbene-catalyzed formal[3+3]annulation of ynals with N-Ts indolin-3-ones under the oxidation condition affording the functionalized pyrano[3,2-b]indol-2-ones.The alkynyl acylazoliums via the combination of a carbene with ynals in the presence of oxidate proved to be the important intermediates for the success of this transformation.This method features a broad substrate scope and mild conditions,including axially chiral skeletons with suitable substitutions.

Electrochemical Cascade Annulation for the Synthesis of 3-Sulfanylquinoline Derivatives under Mild Conditions

An efficient electrochemical approach has been developed for the construction of 3-sulfanylquinoline derivatives by treating phenylethynylbenzoxazinanones with disulfides in an undivided cell.The protocol provided a convenient route to functionalized quinolines with good functional group tolerance.Moreover,it does not require any metal catalysts or additives,furnishing a series of biologicalquinolines inmoderatetogoodyields.

Rh(Ⅲ)-Catalyzed sequential ring-retentive/-opening [4+2]annulations of 2H-imidazoles towards full-color emissive imidazo[5,1-a]isoquinolinium salts and AIE-active non-symmetric 1,1-biisoquinolines

Rhodium-catalyzed C4aryl-H activation and ring-retentive annulation of 2H-imidazoles with internal alkynes to build imidazo[5,1-a]isoquinolinium salts with high yields and broad scope has been disclosed.These novel salts serve as new full-color emissive fluorophores(433-633 nm),just by simply modifying the substituents on C3 and C4 positions of isoquinoline ring.Furthermore,these salts can undergo ring-opening C5_(aryl)-H activation/annulation with a different alkyne to form non-symmetric and AIE-active1,1-biisoquinolines,where NH_(4)OAc plays an indispensable role that accounts for Hofmann elimination and imine formation,leading to an unprecedented imine dance:cyclic imine→N-alkenyl imine→NH imine.The15N labelling experiments indicate that the 2ndannulation includes two pathways:N-exchange(major)and N-retention(minor).

Phosphine-Catalyzed [4+3] Annulation Reaction of Indole Derivatives with MBH Carbonates:A Facile Access to Indole-1,2-fused 1,4-Diazepinones and Azepines

A phosphine-catalyzed [4+3] annulation between dinucleophilic indole derivatives and Morita−Baylis−Hillman (MBH) carbonates was discovered by using the N1 and N4′/C4′ nucleophilicities of the indole precursors,in which indoles act as four atom synthons. This protocol provides an efficient and facile access to indole-1,2-fused 1,4-diazepinones and azepines in good to high yields in one step,which illustrates potential synthetic utilities in drug discovery.

Chemoselective synthesis of α-carboline derivatives via hypervalent iodine-catalyzed [3+3] annulation under metal-free conditions

A strategy for the synthesis ofα-carboline derivatives from indole-3-carboxaldehydes and 3-aminocyclohex-2-enones under metal-free conditions has been developed.The combination use of phenyliodine(Ⅲ)diacetate(PIDA)and benzoic acid could significantly facilitate the corresponding[3+3]annulation process.This newly developed strategy featured unextraordinary chemoselectivity,good functional group tolerance and the preservation of the carbonyl group of the ketone substrates,which offers the possibility for further transformation of the products.

Ni–Al Bimetal-Catalyzed Tertiary C(sp^(3))–H Activation for Dual C–H Annulation of Formamides with Alkynes

3d-Metal-catalyzed tertiary C(sp^(3))–H bond activation has been a formidable challenge.Herein,a tertiary C(sp^(3))–H bond is smoothly activated by Ni–Al bimetallic catalysts for dual C–H annulation of formamides with alkynes,delivering a series of δ-lactams with a quaternary carbon up to 98%yield.Various tertiary C(sp^(3))–H bonds such as noncyclic,monocyclic and bridged-ring tertiary C(sp^(3))–H bonds are all compatible with the reaction.

Synthesis of 9,10-Phenanthrenes via Rh(III)-Catalyzed[4+2]Annulation of 2-Biphenylboronic Acids with Diazo Compounds

A Rh(III)-catalyzed,transmetalation triggered C—H activation/annulation of 2-biphenylboronic acids with diazo compounds fromβ-keto esters or 1,3-dicarboxylates has been developed,leading to the synthesis of two kinds of 9,10-phenanthrenes.Notably,a rhodacyle was synthesized by treating the rhodium catalyst with stoichiometric amounts of 2-biphenylboronic acids and pyridine,which was further verified to be active for the catalytic system.The reactions proceeded under redox-neutral and air-tolerant conditions to produce a series of all-carbon six-membered rings with high efficiency.

TBAI/H_(2)O-cooperative electrocatalytic decarboxylation coupling-annulation of quinoxalin-2(1H)-ones with N-arylglycines

The first example of TBAI/H_(2)O cooperative electrocatalytic coupling-annulation of quinoxalin-2(1H)-ones with N-arylglycines was developed. A broad range of tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones were obtained in good to excellent yields with exclusive chemoselectivities and excellent regioselectivities. The H-hydrogen bond served as a key factor for the electrocatalytic production of aminomethyl radical at lower oxidative potential.

Derivation of Benzothiadiazine-1,1-dioxide Scaffolds via Transition Metal-Catalyzed C-H Activation/Annulation

Comprehensive Summary Benzothiadiazine-1,1-dioxide scaffold is bioactive framework with wild utility and applications.Synthesis of benzothiadiazine-fused isoquinoline derivatives and spiro benzothiadiazine derivatives through transition metal-catalyzed C—H activation/annulation was reported.3-Phenyl-2H-benzothiadiazine-1,1-dioxide was used as the reaction substrate,and vinylene carbonate and 4-diazopyrazolone were used as the coupling reagents,respectively.This strategy provides straightforward access to complex N-heterocycles in a highly efficient and simple manner.

π-Extension of Isoindigos(IIDs)through C—H/N—H Activation and Alkyne Annulation

Isoindigo(IID)is widely used as organic dye and conjugated unit in opto-electronic materials.Functionalization of IID to increase its structural complexity is demanding for obtaining diversity properties.Herein,we developed a direct C-H/N-H activation method of IIDs via double alkyne annulations and synthesizedπ-extended IIDs with two pairs of 5/7 membered rings.The structure of theπ-extended IIDs was characterized and confirmed by^(1)H NMR,^(13)C NMR,HRMS and X ray crystal analysis.Their physical properties were characterized by UV-vis absorption,cyclic voltammetry and thermogravimetric analysis.The absorption coefficient of the annulated products enhanced significantly compared with the non-annulated analogue.

Facile synthesis and functionalization of fluoranthenes via intramolecular[4+2]annulations between thiophenes and alkynes

Fluoranthenes have attracted tremendous attention due to their unique optoelectronic properties and extensive applications.Although several synthetic methodologies have been developed for the preparation of fluoranthene derivatives,it is still unfavorable to functionalize the fluoranthene framework at different positions due to the relatively low selectivity and reactivity.Herein,a catalyst-free intramolecular[4+2]annulation between thiophenes and alkynes is developed towards the synthesis of fluoranthenes.Altogether 20 examples have been demonstrated using this method.Various functional groups can be precisely introduced into the fluoranthene skeleton at different positions by simply tuning the substituents on the thiophenes and alkynes.The conjugation of the fluoranthene can be facilely extended through different directions.Furthermore,the feasibility of this[4+2]annulation reaction is also investigated by density functional theory calculations.Therefore,this protocol provides not only a synthetic methodology towards fluoranthenes with substituents functionalized at different positions,but also an effective pathway to construct large polycyclic aromatic hydrocarbons containing fluoranthene moieties.

Electrochemical radical annulation of 2-alkynyl biaryls with diselenides under catalyst-and chemical oxidant-free conditions

A facile and efficient electrochemical method for sustainable constructing both selanyl phenanthrenes and selanyl polycyclic heteroaromatics(32 examples,71%-97%yields)through the radical annulation of 2-alkynyl biaryls and 2-heteroaryl-substituted alkynyl benzenes with diselenides at ambient temperature under additive-,chemical oxidant-,catalyst-free and mild conditions was established.

Theoretical Investigation of the Mechanism of Rh(III)-catalyzed Annulation of 2-Biphenylboronic Acid with Activated Alkene

The mechanism is investigated for Cp^(tBu)Rh(OH)_(2)-catalyzed annulation of 2-biphenylboronic acid with three activated alkenes using M06-2X functional.The reaction comprises transmetalation via two steps and following C-H activation producing reactive Rh-biphenyl complex with two Rh—Cσbonds.After the coordination/insertion of alkenes,respective fused or bridged cyclic products are yielded depending on different alkenes accompanied by the release of CptBuRh.The promotion of Cp^(tBu)Rh(OH)_(2) lies in the barrier decrease of transmetalation and C-H activation ready for coordination/insertion ensuring the smooth progress of common rate-limiting reductive elimination.The stereoselective transfer and ring rotation are specific for benzoquinone and cyclopropenone.The role of Rh(III)catalyst and release of Rh(I)is supported by Multiwfn analysis on frontier molecular orbital(FMO)of specific transiton states(TSs)and Mayer bond order(MBO)value of vital bonding,breaking.

Iron-catalyzed[4+2]annulation of amidines with α,β-unsaturated ketoxime acetates toward 2,4,6-trisubstituted pyrimidines

An iron-catalyzed[4+2]annulation of amidines with α,β-unsaturated ketoxime acetates is described.This strategy employs amidines as CN units and provides a new protocol for the construction of 2,4,6-trisubstituted pyrimidines under batch and continuous flow conditions in moderate to good yields,exhibiting good functional group tolerance,scalability and operational simplicity.

Cooperative Dual Organocatalytic Asymmetric Decarboxylative[4+3]Annulations with Benzoxazinanones

The cooperative catalysis of an achiral Lewis base and a chiral N-heterocyclic carbene(NHC)enables a highly enantioselective[4+3]annulation of benzoxazinanones with isatin-derived enals.DMAP serves as a nucleophilic Lewis base to promote decarboxylation of benzoxazinanones,which leads to azaortho-xylylene intermediates that undergo[4+3]annulations with NHC-bound homoenolates.This method breaks the substrate scope limitation of transition-metal-catalyzed variants,thus a broader range of benzoxazinanones are tolerated,and provides a straightforward entry to enantioenriched spirooxindoles in high structural diversity.