Silver-Promoted Oxidative Cyclization of 1,6-Enynes: Highly Regioselective Synthesis of Phosphorated Fluorene Derivatives

Base-Mediated and Silver-Catalyzed Divergent Synthesis of Hydroxynaphthalenamides and Phosphorylated Dihydronaphthylamides from Enone-Oxazolones

An efficient divergent approach to functionalized naphthalene derivatives, the naphthalenamides, via base-mediated and silver-catalyzed cyclization has been developed using enone-oxazolones as the precursors. This protocol utilized base in methanol with heating to construct the corresponding hydroxynaphthalenamides 2 by a C-C bond formation, oxazolone ring-opening, and aromatization in good yields. On the other hand, phosphorylated dihydronaphthylamides 3 were generated by using H-phosphonate as the phosphonating reagent in a silver-catalyzed cyclization involving the phospha-1,4-addition/intramolecular ring closure with concomitant C-P/C-C bond formation in good yields.

Copper-Catalyzed Radical Hydrazono-Phosphorylation of Alkenes

An efficient copper-catalyzed radical hydrazono-phosphorylation of alkenes with hydrazine derivatives and diarylphosphine oxides is described. The reaction provides a general and convenient method toward the synthesis of diverse β-hydrazonophosphine oxides in satisfactory yields. Based on conducted mechanistic experiments, a mechanism involving Ag-catalyzed oxidative generation of phosphinoyl radicals and subsequent addition to alkenes followed by Cu-assisted hydrazonation is proposed. Moreover, the practicability of the reaction is successfully demonstrated by its successful application on a gram scale.

Photoinduced Phosphorylation/Cyclization of Cyanoaromatics for Divergent Access to Mono- and Diphosphorylated Polyheterocycles

The visible-light-driven switchable phosphorylation of cyanoaromatics with the 1,6-enyne moiety for the diverse and selective synthesis of phosphorylated polyheterocycles, including phosphorylated aminophosphonates, iminophosphonates, and ketones, has been described. Importantly, these photocatalytic transformations feature good functional group tolerance and high regio- and chemoselectivities under mild reaction conditions. These findings might stimulate the exploration of new photocatalytic utilizations of P(O)-H compounds by employing CN-containing substrates as the radical acceptors.

Dibenzocycloheptanones construction through a removable P-centered radical: synthesis of allocolchicine analogues

Dibenzocycloheptanones containing a tricyclic 6–7–6-system are present in numerous biologically active natural molecules. However, the simple and efficient preparation of derivatives containing a dibenzocycloheptanone scaffold remains difficult to date. Herein, we report a versatile strategy for the construction of these challenging seven-membered rings using a 7-endo-trig cyclization which is initiated by a phosphorus-centered radical. This approach provides a step-economical regime for the facile assembly of a wide range of phosphorylated dibenzocycloheptanones. Remarkably, we also have devised a traceless addition/exchange strategy for the preparation of dephosphorylated products at room temperature with excellent yields. Therefore, this protocol allows for the concise synthesis of biorelevant allocochicine derivatives.

Dibenzocycloheptanones containing a tricyclic 6–7–6-system are present in numerous biologically active natural molecules.

Highly Regioselective Tandem Reaction of Ene-Yne-Oxazolones Induced by H-Phosphonates: Construction of Phosphinylindane Derivatives

A highly regioselective divergent approach for the phosphine-containing indane/indene derivatives from the ene-yne-oxazolone precursors was reported. An insight into the reaction mechanism involving the phospha-1,4-addition followed by 5-exo-dig ring closure with a concomitant C-P/C-C bond formation was also proposed. This promising protocol utilized H-phosphonate as the phosphonating reagent in a silver-catalyzed or base-mediated cascade cyclization to construct the corresponding phosphorylated spiroindenoxazolones and amidoindenes, respectively, in good yields (up to 88% yield).

PhI(OAc)2-Mediated Dihalogenative Cyclization of 1,6-Enyne with Lithium Halide

The dihalogenative cyclization of 1,6-enyne with the assistance of PhI(OAc)₂ and lithium halide is presented. A plausible radical mechanism is proposed, which consists of addition of halogen radical to alkene, 5-exo-dig radical cyclization of enyne and halogenation via radical coupling. The alkenyl- and alkyl-halide groups in the resulted pyrrolidine products have been demonstrated to be facile handles for further transformations.

Fluorene-Based Multicomponent Reactions

Fluorene and fluorenone are privileged structures with extensive utility in both materials science and drug discovery. Here, we describe syntheses of those moieties through isocyanide-based multicomponent reactions (IMCRs) and the incorporation of the products in diverse and complex derivatives that can be further utilized. We performed six different IMCRs, based on the dual functionality of 9-isocyano-9H-fluorene, and we describe 23 unprecedented adducts.

Catalysis and regioselectivity in hydrofunctionalization reactions of unsaturated carbon bonds. Part III

The review addresses the possibility of obtaining Markovnikov and anti-Markovnikov isomers in the reactions of unsaturated hydrocarbons with organophosphorus and organosulfur compounds having P–H and S–H bonds using metal salts or complexes as catalysts.

The bibliography includes 247 references.

Silver(I)-Catalyzed Enyne Cyclization/Aromatization of Alkyne-Tethered Cyclohexadienones to Access Meta-Substituted Phenols

Herein we report a highly regioselective silver(I)-catalyzed intramolecular annulation of alkyne-tethered cyclohexadienones to access meta-substituted phenols with enone functionality, which are difficult to synthesize from conventional methods. The reaction proceeds via intramolecular 1,6-enyne cyclization followed by aromatization and subsequent oxetene ring rearrangement. This strategy has also been compatible with a wide range of C-tethered cyclohexadienones to afford indanes in high yields. The unique functionality of products allows further transformations to expand the diversity.

Photo-driven haloazidation cyclization of 1,5-enynes having cyano groups with TMSN3 and NIS/NCS/NBS under metal-free conditions

A visible-light-driven three-component haloazidation cyclization of 1,5-enynes having cyano groups with TMSN₃ and N-iodo(bromo/chloro)succinimide (NIS/NCS/NBS) under metal-free conditions was developed.

Divergent synthesis of N-heterocyclic 1,6-enynes through a zinc-catalyzed decarboxylative A3 reaction

A zinc-catalyzed decarboxylative A³ reaction of cyclic amino acids, α,β-unsaturated aldehydes and terminal alkynes has been developed. A series of functionalized N-heterocyclic 1,6-enynes have been successfully obtained with excellent regioselectivities through this novel approach. In addition, the utility of this straightforward process is demonstrated by the preparation of a polycyclic nitrogen-containing heterocyclic compound.

Oxidative tandem annulation of 1-(2-ethynylaryl)prop-2-en-1-ones catalyzed by cooperative iodine and TBHP

Metal-free I₂-catalyzed tandem annulation of 1,6-enynes to access 1H-cyclopropa-[b]naphthalene-2,7-diones using TBHP is presented.

Visible-light-mediated hydrodehalogenation and Br/D exchange of inactivated aryl and alkyl halides with a palladium complex

Photo-induced radical reductive dehalogenation of inactivated aryl/alkyl bromides and chlorides with a palladium complex is described. Reductive cyclization, dehalogenative deuteration, and radical addition process can be achieved smoothly.

Iron-catalyzed reductive cyclization reaction of 1,6-enynes for the synthesis of 3-acylbenzofurans and thiophenes

A facile synthesis of 3-acylbenzofurans and thiophenes via iron(ii)-catalyzed reductive cyclization of 1,6-enynes has been developed.

One-pot synthesis of polyfunctionalized quinolines via a copper-catalyzed tandem cyclization

An efficient one-pot approach for the synthesis of polyfunctionalized quinolines was developed via a sequence of copper-catalyzed coupling reaction/propargyl-allenyl isomerization/aza-electrocyclization. Easily available starting materials, mild conditions, and a wide substrate scope make this approach potentially useful.

One-pot bifunctionalization of unactivated alkenes, P(O)–H compounds, and N-methoxypyridinium salts for the construction of β-pyridyl alkylphosphonates

An efficient phosphono-heteroarylation of unactivated alkenes was developed through a one-pot bifunctionalization process to give access to β-pyridylphosphine structural motifs.

Phosphinoyl-functionalization of unactivated alkenes through phosphinoyl radical-triggered distal functional group migration

Reported herein is a novel, mild, and practical protocol for the radical-mediated phosphinoyl-functionalization of unactivated alkenes through distal functional group migration.

Silver-Catalyzed Radical-Involved Cascade Cyclization of Diphenylphosphine with Cinnamamides: Access to 2-Phosphinoyl-3H-pyrrolo[1,2-a]indoles

A Ag-catalyzed phosphorus radical promoted cyclization of cinnamamides to give exclusively 2-phosphinoyl-3H-pyrrolo[1,2-a]indoles derivatives via a 5-endo-trig manner is described. This novel reaction leads to the simultaneous formation of C-C and C-P bonds in one step with excellent chemo- (only 5-endo) and diastereoselectivity (dr >20:1) under mild conditions in moderate to good yields.

Radical cascade cyclization of 1,n-enynes and diynes for the synthesis of carbocycles and heterocycles

This review highlights recent advances in radical cascade cyclization of 1,n-enynes and diynes for the construction of carbo- and heterocycles.

Photocatalyzed cascade oxidative annulation of propargylamines and phosphine oxides

A novel photocatalyzed radical cascade reaction was developed for the synthesis of phosphorylated heterocycles. One of the phosphorylated quinolines was employed as an electron-transporting material for fabricating organic light-emitting diodes displaying excellent performances with a maximum external quantum efficiency of 21.9%.

Silver-mediated radical 5-exo-dig cyclization of 2-alkynylbenzonitriles: synthesis of phosphinylated 1-indenones

A new silver-mediated 5-exo-dig cyclization of 2-alkynylbenzonitriles with disubstituted phosphine oxide and H₂O has been developed.

Visible-Light-Induced Cascade Reaction of Isocyanides and N-Arylacrylamides with Diphenylphosphine Oxide via Radical C-P and C-C Bond Formation

An effective photoredox-mediated tandem phosphorylation/cyclization reaction of diphenylphosphine oxide with three types of radical acceptors leads to P(O)Ph₂-containing phenanthridines, isoquinolines, and indolin-2-ones by formation of both C-P and C-C bonds. [Ir(ppy)₂(dtbpy)]PF₆ (1 mol %) was used as the catalyst, CsF or Cs₂CO₃ as the base, and K₂S₂O₈ as the oxidant. A series of functional groups can be tolerated at room temperature. Moderate to good yields were generated.

Acid-Catalyzed Multicomponent Tandem Double Cyclization: A One-pot, Metal-free Route to Synthesize Polyfunctional 4,9-Dihydropyrrolo[2,1-b]quinazolines

An acid-catalyzed multicomponent tandem double cyclization protocol has been developed for the synthesis of polyfunctional 4,9-dihydropyrrolo[2,1-b]quinazolines from simple and readily available arylglyoxal monohydrates, 2-aminobenzylamine, and trans-β-nitrostyrenes. This practical and metal-free reaction proceeds through an imine formation/cyclization/Michael addition/Henry cyclization protocol, resulting in the construction of four new bonds and two ring moieties directly in one pot.

Metal-free oxidative hydrophosphinylation of 1,7-enynes

A new metal-free oxidative hydrophosphinylation of 1,7-enynes for forming polyfunctionalized 3,4-dihydroquinolin-2(1H)-ones has been realized using readily accessible diarylphosphine oxide and TBPB as an oxidant.

Silver-promoted cinnamamidyl radical-mediated oxidative cascade cyclization: highly regioselective synthesis of phosphorylated azaspiro[4.5]decenones

A novel cinnamamidyl radical-mediated oxidative cascade cyclization to synthesize phosphorylated azaspiro[4.5]decenones has been developed.

Copper-catalyzed cycloaddition between hydrogen phosphonates and activated alkenes: synthesis of phosphonoisoquinolinediones

A new and general method for the synthesis of phosphonoisoquinolinediones has been achieved through copper-catalyzed phosphonation–cyclization of various methacryloylbenzamides with P(O)H compounds.