Dual Roles of β‑Oxodithioesters in the Copper-Catalyzed Synthesis of Benzo[<i>e</i>]pyrazolo[1,5‑<i>c</i>][1,3]thiazine Derivatives

A facile and efficient method for the chemoselective synthesis of benzo­[<i>e</i>]­pyrazolo­[1,5-<i>c</i>]­[1,3]­thiazine derivatives has been developed by tandem Ullmann coupling reactions of β-oxodithioesters (ODEs) with 3-(2-bromoaryl)-1<i>H</i>-pyrazoles in C–S bond formation manner, in which ODEs play dual roles as both a substrate and a ligand. A series of benzo­[<i>e</i>]­pyrazolo­[1,5-<i>c</i>]­[1,3]­thiazine derivatives were provided in good to excellent yields with CuI as the copper source in the presence of NaOH in CH₃CN at 80 °C under a N₂ atmosphere

Yb(OTf)₃‑Mediated Access to Furans from β‑Ketothioamides via Eschenmoser Sulfide Contraction Reaction

A mild and straightforward synthetic protocol for construction of a furan skeleton promoted by Yb­(OTf)₃ from β-ketothioamides and arylglyoxals has been developed at room temperature. Importantly, this protocol involves a tandem sequence that includes aldol condensation, N-cyclization, ring opening, O-cyclization, S-cyclization, and Eschenmoser sulfide contraction

Direct Construction of 2‑Aryliminochromenes from Arynes, <i>N</i>,<i>S</i>‑Keteneacetals, and DMF

A concise and direct synthetic strategy for the construction of 2-aryliminochromene skeleton by cascade three-component coupling reaction of arynes, <i>N</i>,<i>S</i>-keteneacetals, and DMF in good yields has been disclosed. The process demonstrates the first example of aryne chemistry combined with <i>N</i>,<i>S</i>-keteneacetals. Using this strategy, an expeditious synthesis of biologically important arylimino-2<i>H</i>-chromene-3- carboxamides was achieved

When Ethyl Isocyanoacetate Meets Isatins: A 1,3-Dipolar/Inverse 1,3-Dipolar/Olefination Reaction for Access to 3‑Ylideneoxindoles

A new CuI/1,10-phen-catalyzed reaction for the synthesis of 3-ylideneoxindoles from readily available isatins and ethyl isocyanoacetate, in which ethyl isocyanoacetate acts as a latent two-carbon donor like the Wittig reagent, is reported. A tandem procedure including 1,3-dipolar cycloaddition/inverse 1,3-dipolar ring opening/olefination allows the preparation of 3-ylideneoxindoles with broad functional group tolerance

Three-Component Cascade Annulation of β‑Ketothioamides Promoted by CF₃CH₂OH: A Regioselective Synthesis of Tetrasubstituted Thiophenes

A rapid and highly efficient method for the regioselective synthesis of thiophene derivatives has been developed by annulation of β-ketothioamides with arylglyoxals and 5,5-dimethyl-1,3-cyclohexanedione in CF₃CH₂OH within 15 min. The present synthesis has several desirable features, such as high regioselectivity, a concise one-pot protocol, short reaction time, and easy purification. This methodology provides an alternative approach for easy access to tetrasubstituted thiophenes via a one-pot cascade reaction without other additives

Three-Component Cascade Annulation of β‑Ketothioamides Promoted by CF₃CH₂OH: A Regioselective Synthesis of Tetrasubstituted Thiophenes

A rapid and highly efficient method for the regioselective synthesis of thiophene derivatives has been developed by annulation of β-ketothioamides with arylglyoxals and 5,5-dimethyl-1,3-cyclohexanedione in CF₃CH₂OH within 15 min. The present synthesis has several desirable features, such as high regioselectivity, a concise one-pot protocol, short reaction time, and easy purification. This methodology provides an alternative approach for easy access to tetrasubstituted thiophenes via a one-pot cascade reaction without other additives

Four-Component Cascade Heteroannulation of Heterocyclic Ketene Aminals: Synthesis of Functionalized Tetrahydroimidazo[1,2‑<i>a</i>]pyridine Derivatives

An efficient and straightforward four-component synthetic protocol has been developed to synthesize imidazo­[1,2-<i>a</i>]­pyridines and imidazo­[1,2,3-<i>ij</i>]­[1,8]­naphthyridine derivatives incorporating medicinally privileged heterosystems from heterocyclic ketene aminals, aldehydes, diketene, and amines via cascade reactions, including diketene ring-opening, Knoevenagel condensation, aza–ene reaction, imine–enamine tautomerization, cyclocondensation, and intramolecular S_NAr. This strategy can provide an alternative approach for easy access to the highly substituted imidazo­[1,2-<i>a</i>]­pyridine derivatives in moderate to good yields using four simple and readily available building blocks under mild conditions. Importantly, the unusual splitting peaks in the ¹H NMR spectra of the products derived from heterocyclic ketene aminals with an <i>o</i>-halogen atom on the aryl ring were explained reasonably by varying the temperature in NMR analysis

Direct Solvent-Free Regioselective Construction of Pyrrolo[1,2‑<i>a</i>][1,10]phenanthrolines Based on Isocyanide-Based Multicomponent Reactions

A novel efficient one-pot four-component regioselective synthesis of pyrrolo[1,2-<i>a</i>][1,10]phenanthrolines in excellent yields has been developed by 1,3-dipolar cycloaddition of aldehydes, malononitrile, and isocyanides with 1,10-phenanthroline under solvent-free conditions within 3 min without using any catalyst or activation. The products were preliminarily investigated as chromogenic and fluorescent sensors for Cu²⁺ ions

Modulating the Reactivity of Functionalized <i>N</i>,<i>S</i>-Ketene Acetal in MCR: Selective Synthesis of Tetrahydropyridines and Thiochromeno[2,3-<i>b</i>]pyridines via DABCO-Catalyzed Tandem Annulation

An efficient and straightforward three-component synthetic protocol was developed to synthesize 1,2,3,4-tetrahydropyridine derivatives or thiochromeno­[2,3-<i>b</i>]­pyridine derivatives from β-aroylthioacetanilides or β-(2-haloaroyl)­thioacetanilides, aldehydes, and aroyl acetonitriles via DABCO-catalyzed tandem [3 + 2 + 1] annulation and S_NAr reaction. This synthetic approach has the prominent features of high chemo-, stereo- (or enantio-), and unusual regioselectivity. In the domino processes, at least seven reactive sites were involved, and up to three covalent bonds and one functionalized pyridine ring were generated. This facile and efficient reaction is a quite general for the preparation of tetrahydropyridine derivatives or thiochromeno­[2,3-<i>b</i>]­pyridine derivatives

Modulating the Reactivity of Functionalized <i>N</i>,<i>S</i>-Ketene Acetal in MCR: Selective Synthesis of Tetrahydropyridines and Thiochromeno[2,3-<i>b</i>]pyridines via DABCO-Catalyzed Tandem Annulation

An efficient and straightforward three-component synthetic protocol was developed to synthesize 1,2,3,4-tetrahydropyridine derivatives or thiochromeno­[2,3-<i>b</i>]­pyridine derivatives from β-aroylthioacetanilides or β-(2-haloaroyl)­thioacetanilides, aldehydes, and aroyl acetonitriles via DABCO-catalyzed tandem [3 + 2 + 1] annulation and S_NAr reaction. This synthetic approach has the prominent features of high chemo-, stereo- (or enantio-), and unusual regioselectivity. In the domino processes, at least seven reactive sites were involved, and up to three covalent bonds and one functionalized pyridine ring were generated. This facile and efficient reaction is a quite general for the preparation of tetrahydropyridine derivatives or thiochromeno­[2,3-<i>b</i>]­pyridine derivatives