Organocatalytic Direct <i>N</i>‑Acylation of Amides with Aldehydes under Oxidative Conditions

The direct oxidative <i>N</i>-acylation reaction of primary amides with aryl/α,β-unsaturated aldehydes was achieved in the presence of azolium salt <b>C3</b> and an inorganic base using 3,3′,5,5′-tetra-<i>tert</i>-butyldiphenoquinone as the oxidant, thus providing an efficient approach for the synthesis of three types of imide compounds including <i>N</i>-sulfonylcarboxamides, <i>N</i>-sulfinylcarboxamides, and dicarboxyimides in good yield

Crossover-Annulation/Oxygenation Approach to Functionalized Phenanthridines by Palladium–Copper Relay Catalysis

A tandem crossover-annulation and oxygenation process of conjugated enediyne-acids and <i>ortho</i>-alkynylanilines was achieved by palladium–copper relay catalysis under an oxygen atmosphere, giving access to the three-component assembly of 9-acylphenanthridine compounds

Pd-Catalyzed Branching Cyclizations of Enediyne-Imides toward Furo[2,3‑<i>b</i>]pyridines

The convergent synthesis of a class of enediyne-imides as well as their palladium-catalyzed branching cyclizations, which can be accomplished in two ways leading to a set of polysubstituted furo­[2,3-<i>b</i>]­pyridines upon using the <i>N</i>-tosyl carboxamide moiety as an <i>N</i>,<i>O</i>-bisnucleophile, are presented

Tuning of Copper-Catalyzed Multicomponent Reactions toward 3‑Functionalized Oxindoles

A tunable copper-catalyzed azide–alkyne cycloaddition (CuAAC)-initiated multicomponent reaction strategy for the construction of 3-functionalized indolin-2-ones is reported. Upon controlling the ring opening of four-membered <i>O</i>-heterocyclic intermediates, this unique method enables the divergent derivatization of <i>N</i>-protected isatins to give three-component (3-CR) and four-component (4-CR) adducts, respectively

Pd-Catalyzed Branching Cyclizations of Enediyne-Imides toward Furo[2,3‑<i>b</i>]pyridines

The convergent synthesis of a class of enediyne-imides as well as their palladium-catalyzed branching cyclizations, which can be accomplished in two ways leading to a set of polysubstituted furo­[2,3-<i>b</i>]­pyridines upon using the <i>N</i>-tosyl carboxamide moiety as an <i>N</i>,<i>O</i>-bisnucleophile, are presented

Coupling and Decoupling Approach Enables Palladium-Catalyzed Aerobic Bimolecular Carbocyclizations of Enediynes to 2,6-Diacylnaphthalenes

A formal palladium-catalyzed aerobic bimolecular carbocyclization reaction of (<i>Z</i>)-hexa-1,5-diyn-3-ene scaffolds has been successfully developed for the construction of 2,6-diacylnaphthalenes, wherein copper salts play a critical role in accomplishing the oxygenative homo- and hetero-dimerization processes of readily accessible enediyne–carboxylic acids and esters, respectively. The enediyne dimerization protocol provides a flexible and regiospecific approach to a variety of functionalized naphthalenes with up to six differentiated substituents in good yields by using a directing-group-assisted coupling and decoupling strategy. Mechanistic studies indicated that the two oxygen atoms being selectively incorporated into the crossover-annulation products of enediynecarboxylic acid and ester directly originate from atmospheric molecular oxygen and H₂O, respectively

Three-Component Assembly of Conjugated Enyne Scaffolds via <i>E</i>-Selective Olefination of Ynals

Benefited by the accessible ynamido–lithium intermediates <b>Ib</b> from a Cu-catalyzed azide–alkyne cycloaddition in the presence of stoichiometric amounts of LiOH, a mild and flexible three-component route to conjugated enyne scaffolds was successfully achieved via a formal <i>E</i>-selective olefination strategy

Three-Component Functionalized Dihydropyridine Synthesis via a Formal Inverse Electron-Demand Hetero-Diels–Alder Reaction

A mild three-component synthetic approach to versatile 2-amino-1,4-dihydropyridines from terminal alkynes, sulfonyl azides, and <i>N</i>-sulfonyl-1-aza-1,3-butadienes was successfully developed and relied on the in situ generation of metalated ynamide intermediates <b>Ib</b> to achieve a formal inverse electron-demand hetero-Diels–Alder reaction. Experimental results suggest that alkali metal cations (Li⁺ and Cs⁺ ions) might play a critical role to achieve the cycloaddition process

Copper-Catalyzed Tandem Reaction of Terminal Alkynes and Sulfonyl Azides for the Assembly of Substituted Aminotriazoles

A simple combination of CuI/LiO<i>t</i>Bu/DMF enables the tandem Huisgen [3 + 2] cycloaddition/amidation reaction of terminal alkynes and sulfonyl azides to 5-sulfamide-1-(<i>N</i>-sulfonyl)-1,2,3-triazoles <b>I</b>, which can undergo an alkylation/desulfonation sequence to deliver highly substituted aminotriazoles <b>II</b> by one-pot or one-pot, two-step procedures

Bifuctional Amino-Squaramides Catalyzed Asymmetric Spiroannulation Cascades with Aliphatic β,γ-Unsaturated α-Keto Esters: Controlling an Aldehyde Enolate

A quinidine-derived squaramide <b>Ib</b> catalyzed cyclization reaction of β-oxo aldehydes <b>1</b> and aliphatic or aromatic β,γ-unsaturated α-keto ester <b>2</b> is described. Using cyclic aldehyde substrates, this procedure provided a promising approach to a variety of spiro-3,4-dihydropyrans bearing three continuous quaternary and tertiary stereocenters in moderate to good yield with high stereoselectivities. Substituents on the nitrogen atoms of the squaramide moiety of the catalyst proved crucial to the reaction outcome. The stereochemistry of the three newly formed chiral centers (<i>trans</i>-selective) of the major product indicates a Micheal addition/hemiacetalization domino sequence for the present annulations