Practical Synthesis of Phthalimides and Benzamides by a Multicomponent Reaction Involving Arynes, Isocyanides, and CO₂/H₂O

Transition-metal-free multicomponent reactions involving arynes and isocyanides with either CO₂ or H₂O have been reported. With CO₂ as the third component, the reactions resulted in the formation of <i>N</i>-substituted phthalimides. The utility of water as the third component furnished benzamide derivatives in moderate to good yields. These reactions took place under mild conditions with broad scope

N‑Heterocyclic Carbene-Catalyzed Aza-Michael–Mannich–Lactamization Cascade for the Enantioselective Synthesis of Pyrazoloquinolin-3-ones

The enantioselective synthesis of functionalized pyrazoloquinolin-3-ones via N-heterocyclic carbene-catalyzed cascade reaction of α-bromoenals with 2-aminoaryl N-tosyl hydrazones is reported. The in situ-generated α,β-unsaturated acylazoliums underwent an aza-Michael–Mannich–lactamization sequence to afford the tricyclic products bearing three contiguous stereocenters, including a sterically demanding quaternary stereocenter with high enantioselectivity. The unprotected amine-triggered aza-Michael pathway over the competing amidation pathway is noteworthy

Facile Synthesis of γ‑Ketophosphonates by an Intermolecular Stetter Reaction onto Vinylphosphonates

The atom-economic and practical N-heterocyclic carbene (NHC) catalyzed Stetter reaction for the synthesis of γ-ketophosphonates by the reaction of aromatic aldehydes with vinylphosphonates is reported. The NHC derived from <i>N</i>-mesitylimidazolium salt (IMes) was an effective catalyst for this transformation, and the products were formed in moderate to good yields

Employing Arynes in Transition-Metal-Free Monoarylation of Aromatic Tertiary Amines

The highly monoselective N-arylation of aromatic tertiary amines using a transition-metal-free approach using arynes has been developed. The reaction afforded functionalized diaryl amines in moderate to excellent yield. High levels of functional group compatibility especially with halogen containing substrates, dyes and donor–acceptor systems, and high yields of products are the notable features of the present reaction

NHC-Catalyzed Reaction of Enals with Hydroxy Chalcones: Diastereoselective Synthesis of Functionalized Coumarins

The N-heterocyclic carbene-catalyzed annulation of enals with 2′-hydroxy chalcones afford cyclopentane-fused coumarin derivatives with an excellent level of diastereocontrol. The reaction tolerates a broad range of functional groups; 25 examples are given, and a preliminary mechanistic investigation is provided

Efficient Diels–Alder Reaction of 1,2-Benzoquinones with Arynes and Its Utility in One-Pot Reactions

A new protocol for the efficient Diels–Alder reaction of 1,2-benzoquinones with arynes is reported. The aryne generated by the fluoride-induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates undergoes a facile Diels–Alder reaction with 1,2-benzoquinones, affording the dioxobenzobicyclooctadienes in moderate to excellent yields. In addition, this methodology has been applied to the one-pot synthesis of benzoquinoxalinobarrelene and naphthalene derivatives

Employing Arynes for the Generation of Aryl Anion Equivalents and Subsequent Reaction with Aldehydes

Arynes are highly reactive intermediates, which are utilized for the electrophilic arylation of various X–H bonds (X = O, N, S etc.). Herein, a new synthetic strategy is demonstrated, where arynes are converted into aryl anion equivalents by treatment with phosphines and a base. The addition of phosphines to arynes form the phosphonium salts, which in the presence of a carbonate base generates the aryl anion equivalent. Subsequent addition of the aryl anions with aldehydes afforded the secondary alcohols

Synthesis of <i>N</i>‑Aryl β‑Amino Alcohols by Trifluoroacetic Acid Promoted Multicomponent Coupling of Aziridines, Arynes, and Water

A transition-metal-free, three-component coupling involving <i>N</i>-substituted aziridines, arynes, and water promoted by trifluoroacetic acid (TFA) has been reported. The reaction furnished medicinally important <i>N</i>-aryl β-amino alcohol derivatives in moderate to good yields. In addition, the use of azetidines in this reaction afforded <i>N</i>-aryl γ-amino alcohol derivatives

N‑Heterocyclic Carbene-Catalyzed Enantioselective Synthesis of Spiro-glutarimides via α,β-Unsaturated Acylazoliums

NHC-catalyzed enantioselective [3 + 3] spiro-annulation of α,β-unsaturated aldehydes with cyclic β-ketoamides allowing the preparation of synthetically and biologically important spiro-glutarimide derivatives has been reported. The interception of the ketoamides with catalytically generated chiral α,β-unsaturated acylazoliums proceeds in a Michael addition–intramolecular amidation pathway to deliver the spirocyclic products with good yield, diastereoselectivity, and enantioselectivity

Multicomponent Reactions Involving Arynes, Quinolines, and Aldehydes

The multicomponent reaction involving arynes, quinolines, and aldehydes leading to the diastereoselective synthesis of benzoxazino quinoline derivatives in good yields proceeding via 1,4-zwitterionic intermediates is reported. In addition, the synthetic potential of various carbonyl compounds in this reaction as well as the utility of isoquinoline as the nucleophilic trigger has been examined