Copper‐Promoted Annulation of Terminal Alkynes with 2‐Aminopyridines to Assemble 2‐Halogenated Imidazo[1,2‐a]pyridines

Copper‐promoted annulation reactions of terminal alkynes with 2‐aminopyridines have been developed for the synthesis of 2‐halogenated imidazo[1,2‐a]pyridines using copper halide as the halogen source. A variety of substrates survived under the reaction conditions and gave the desired products in good yields. This reaction features advantages such as easily available starting materials, broad substrate scope, and mild reaction conditions.     

One‐pot Combinatorial Synthesis of Benzo[4,5]imidazo‐[1,2‐a]thiopyrano[3,4‐d]pyrimidin‐4(3H)‐one Derivatives

A series of novel fused tetracyclic benzo[4,5]imidazo[1,2‐a]thiopyrano[3,4‐d]pyrimidin‐4(3H)‐one derivatives were synthesized via the reaction of aryl aldehyde, 2H‐thiopyran‐3,5(4H,6H)‐dione, and 1H‐benzo[d]imidazol‐2‐amine in glacial acetic acid. This protocol features mild reaction conditions, high yields and short reaction time.     

Synthesis of Novel Phthalazino[1,2‐b]quinazolinedione Derivatives: Efficient and Practical Reaction of 2‐Amino‐N′‐Arylbenzohydrazides and 2‐Formylbenzoic Acids

This work reported the synthesis of novel phthalazino[1,2‐b]quinazolinedione derivatives through the reaction of 2‐amino‐N′‐arylbenzohydrazides and 2‐formylbenzoic acids in the presence of TsOH in EtOH under reflux conditions.     

Highly efficient AgNO3‐catalyzed approach to 2‐(benzo[d]azol‐2‐yl)phenols from salicylaldehydes with 2‐aminothiophenol, 2‐aminophenol and benzene‐1,2‐diamine

A new, convenient and efficient AgNO₃‐catalyzed strategy for the preparation of 2‐(benzo[d]azol‐2‐yl)phenol derivatives in good to excellent yields (63–98%) is described. The reaction proceeds via condensation/intramolecular nucleophilic addition/oxidation process between substituted salicylaldehydes and 2‐aminothiophenol, 2‐aminophenol or benzene‐1,2‐diamine under mild reaction conditions. Notably, this reaction utilizes cheap AgNO₃ as a readily available and low‐cost benign oxidant at low catalyst loadings with excellent functional group tolerance.     

Facile and Selective Synthesis of 4‐Methyl‐ and 4‐Phenylthiosemicarbazide (=N‐Methyl‐ and N‐Phenylhydrazinecarbothioamide) Derivatives of Benzil (=1,2‐Diphenylethane‐1,2‐dione)

A selective synthesis of 4‐methylthiosemicarbazide (=N‐methylhydrazinecarbothioamide; 4a ) derivatives by reaction with benzil (=1,2‐diphenylethane‐1,2‐dione; 3 ) is described. The reaction conditions determined the condensation product formed. The most important factor was the acid used: in the presence of conc. HCl solution, the open‐chain 2 : 1 compound 1a was exclusively obtained, whereas in the presence of 2M HCl, the cyclic 1 : 1 condensation product 2a was formed. The alcohol used, the presence of H₂O, and the time of heating were additional crucial factors. The new cyclic compound 2a with a MeO group was exclusively formed when working under high‐dilution conditions. The reaction with the 4‐phenyl derivative 4b gave new cyclic compounds as the major products under all conditions used (Scheme).     

NaSO2Ph 催化下1，2-联烯亚砜高产率，高选择性异构化为炔基亚砜

The clean isomerization of 1,2-allenyl sulfoxides in the presence of NaSO2Ph afforded 2-alkynylic phenyl sulfoxides in good yields and selectivities. Although strong base-catalyzed isomerization of allenes to alkynes is known, the mechanism for the current reaction is interesting for the obvious reason that NaSOEPh is a weak base.     

Regioselective and 1,2‐cis‐α‐Stereoselective Glycosylation Utilizing Glycosyl‐Acceptor‐Derived Boronic Ester Catalyst

Regioselective and 1,2‐cis‐α‐stereoselective glycosylations using 1α,2α‐anhydro glycosyl donors and diol glycosyl acceptors in the presence of a glycosyl‐acceptor‐derived boronic ester catalyst. The reactions proceed smoothly to give the corresponding 1,2‐cis‐α‐glycosides with high stereo‐ and regioselectivities in high yields without any further additives under mild reaction conditions. In addition, the present glycosylation method was successfully applied to the synthesis of an isoflavone glycoside.     

(3‐Oxo‐[1,2,4]triazolidin‐1‐yl)bis (butane‐1‐sulfonic acid) functionalized magnetic γ‐Fe2O3 nanoparticles: A novel and heterogeneous nanocatalyst for one‐pot and efficient four‐component synthesis of novel spiro[indeno[1,2‐b]quinoxaline derivatives

The efficient synthesis of novel spiro[indeno[1,2‐b]quinoxaline derivatives via the four‐component condensation of amines, ninhydrin, isatoic anhydride, and о‐phenylenediamine derivatives catalyzed by ( 3‐oxo‐[1,2,4]triazolidin‐1‐yl)bis (butane‐1‐sulfonic acid) supported on γ‐Fe₂O₃ as novel heterogenous magnetic nanocatalyst was described. The novel nanocatalyst was characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), vibrating sample magnetometry (VSM), Field Emission Scanning Electron Microscopy (FE‐SEM), and thermal analysis (TGA‐DTG). The nanoparticles covered by (3‐oxo‐[1,2,4]triazolidin‐1‐yl)bis (butane‐1‐sulfonic acid) showed enhanced catalytic performance in the preparation of spiro[indeno[1,2‐b]quinoxaline derivatives in excellent yields. Moreover, this method showed several advantages such as mild conditions, high yields, easy work‐up, and being environmentally friendly. The catalyst can be easily separated from the reaction mixture by an external magnet, recycled, and reused several times without a noticeable decrease in catalytic activity.     

Isocyanide‐Based Three‐Component Synthesis of Highly Substituted 1,6‐Dihydro‐6,6‐dimethylpyrazine‐2,3‐dicarbonitrile, 3,4‐Dihydrobenzo[g]quinoxalin‐2‐amine,and 3,4‐Dihydro‐3,3‐dimethyl‐quinoxalin‐2‐amine Derivatives

A novel and efficient isocyanide‐based multicomponent reaction between alkyl or aryl isocyanides 1 , 2,3‐diaminomaleonitrile ( 2 ), naphthalene‐2,3‐diamines ( 6 ) or benzene‐1,2‐diamine ( 9 ), and 3‐oxopentanedioic acid ( 3 ) or Meldrum's acid ( 4 ) or ketones 7 was developed for the ecologic synthesis, at room temperature under mild conditions, of 1,6‐dihydropyrazine‐2,3‐dicarbonitriles 5a – 5f in H₂O without using any catalyst, and of 3,4‐dihydrobenzo[g]quinoxalin‐2‐amine and 3,4‐dihydro‐3,3‐dimethyl‐quinoxalin‐2‐amine derivatives 8a – 8g and 10a – 10e , respectively, in the presence of a catalytic amount of p‐toluenesulfonic acid (TsOH) in EtOH, in good to excellent yields (Scheme 1).     

FeCl3‐Mediated Three‐Component Cascade Reaction: An Effective Approach to the Construction of Highly Functionalized Pyrrolo[1,2‐c]quinazolinones

An unexpected FeCl₃‐mediated three‐component cascade reaction has been used to construct structurally diverse pyrrolo[1,2‐c]quinazolinone derivatives with potential biological activities. This method has advantages of mild conditions, simple work‐up, as well as wide substrate scope, which makes it a powerful approach to the synthesis of diverse pyrrolo[1,2‐c]quinazolinones. This cascade reaction involves 1,3‐dipolar cycloaddition between azomethine ylides and allenoates, followed by intramolecular nucleophilic addition in the presence of FeCl₃. The obtained products could be easily transformed into derivatives with the pyrrolo[2,3‐c]quinazoline alkaloid skeleton.     

Revisiting the Hinsberg Reaction: Facile and Expeditious Synthesis of 3‐Substituted Quinoxalin‐2(1H)‐ones under Catalyst‐Free Conditions in Water

Substituted benzene‐1,2‐diamine reacted with various α‐keto esters at 50° under mild conditions for 15 min using H₂O as reaction medium, providing a variety of 3‐substituted quinoxalinone derivatives in excellent yields. The reaction was instantaneous, and products were isolated by simple filtration.     

Novel and Stereospecific Synthesis of (2S)‐3‐(2,4,5‐Trifluorophenyl)propane‐1,2‐diol from D‐Mannitol

A stereospecific synthesis of (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol from D ‐mannitol has been developed. The reaction of 2,3‐O‐isopropylidene‐D ‐glyceraldehyde with 2,4,5‐trifluorophenylmagnesium bromide gave [(4R)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl](2,4,5‐trifluorophenyl)methanol in 65% yield as a mixture of diastereoisomers (1 : 1). The Ph₃P catalyzed reaction of the latter with C₂Cl₆ followed by reduction with Pd/C‐catalyzed hydrogenation gave (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol with >99% ee and 65% yield.     

A Facile,Atom‐Economical,and One‐Pot Pseudo Four‐Component Synthesis of Isoxazolylspiro[diindeno[1,2‐b;2′,1′‐e]pyridine‐11,3′‐indoline]‐2′,10,12‐triones Catalyzed by pTSA

A facile, atom‐economical, and one‐pot pseudo four‐component method for the synthesis of isoxazolylspiro[diindeno[1,2‐b ;2′,1′‐e ]pyridine‐11,3′‐indoline]‐2′,10,12‐trione derivatives ( 14 ) is described. Prominent advantages of this new method are operational simplicity, excellent yields with high purity, short reaction time, easy workup, and mild conditions.     

Selective Synthesis of 1,2‐Diarylpyrrolo[3,4‐b]pyridine‐5,7‐diones via Cyclization Reaction of β‐Enamino Imides with Cinnamaldehydes

The novel 1,2‐diaryl substituted pyrrolo[3,4‐b]pyridine‐5,7‐diones were selectively synthesized in high yields by the base catalyzed cyclization reaction of 3‐arylamino‐1‐methyl‐1H‐pyrrole‐2,5‐diones with cinnamaldehyde and its derivatives in acetonitrile at room temperature. However, when piperidinium trifluoroacetate was employed as catalyst, the reaction afforded a mixture of 1,2‐diaryl and 1,4‐diaryl substituted pyrrolo[3,4‐b]pyridine‐5,7‐diones in comparable yields.     

Two seven‐membered heterocycles with 1,2‐diaza ring N atoms: 3,5,7‐triphenyl‐1,2‐diazacyclohepta‐1(7),2‐diene and 3,7‐bis(2‐hydroxyphenyl)‐5‐phenyl‐1,2‐diazacyclohepta‐1(7),2‐diene

The title compounds, 3,5,7‐triphenyl‐1,2‐diazacyclohepta‐1(7),2‐diene, C₂₃H₂₀N₂, (I), and 3,7‐bis(2‐hydroxyphenyl)‐5‐phenyl‐1,2‐diazacyclohepta‐1(7),2‐diene, C₂₃H₂₀N₂O₂, (II), constitute the first structurally characterized examples of seven‐membered heterocycles with 1,2‐diaza ring N atoms. Compound (I) crystallizes in the space group P, with two independent molecules in the asymmetric unit that differ in the conformation of one of the phenyl rings, while (II) crystallizes in the space group C2/c. The C₅N₂ ring in each of (I) and (II) adopts a twist‐boat conformation. Compound (I) exhibits neither C—H...π interactions nor π–π stacking interactions, whereas (II) shows both intramolecular O—H...N hydrogen bonds and a C—H...π interaction that joins the molecules into an infinite chain in the [010] direction.     

1,2‐Thiazines: One‐Pot Syntheses Utilizing Mono and Diaza Analogs of Sulfones

A one‐pot Michael addition/cyclization/condensation reaction sequence for the regioselective synthesis of 1,2‐thiazines, starting from propargyl ketones and NH‐sulfoximines or NH‐sulfondiimines, has been developed. Under mild and operationally simple reaction conditions previously unprecedented 1,2‐thiazine 1‐imide and 1‐oxide derivatives are formed in good to excellent yields. The products represent heterocyclic building blocks, readily modifiable by a regioselective C?H bond functionalization, classical cross‐coupling reactions, and deprotection.     

An Efficient Method for the Synthesis of 3‐Arylnaphtho[2,3‐f]quinoline‐1,2‐dicarboxylate Derivatives Catalyzed by Yb(OTf)3

A mild and efficient method for the synthesis of 3‐arylnaphtho[2,3‐f]quinoline‐1,2‐dicarboxylate derivatives via Povarov reaction of aromatic aldehyde, anthracen‐2‐amine, and but‐2‐ynedioate is described using Yb(OTf)₃ as catalyst. The features of this procedure are mild reaction conditions, good yields, and operational simplicity.     

Efficient One‐Pot Synthesis of Spiro[indoline‐3,1′‐pyrazolo[1,2‐b] phthalazine] Derivatives via Three‐Component Reaction

An efficient one‐pot synthesis of spiro[indoline‐3,1′‐pyrazolo[1,2‐b]phthalazine] derivatives via three‐component reaction of phthalhydrazide, isatin, and malononitrile (cyanoacetic ester) is described. This new protocol has the advantages of high efficiency, mild reaction conditions, one‐pot procedure, and convenient operation.     

Significant Substituent Effect on the Anomerization of Pyranosides: Mechanism of Anomerization and Synthesis of a 1,2‐cis Glucosamine Oligomer from the 1,2‐trans Anomer

Aminoglycosides containing a 2,3‐trans carbamate group easily undergo anomerization from the 1,2‐trans glycoside to the 1,2‐cis isomer under mild acidic conditions. The N‐substituent of the carbamate has a significant effect on the anomerization reaction; in particular, an N‐acetyl group facilitated rapid and complete α‐anomerization. The differences in reactivity due to the various N‐substituents were supported by the results of DFT calculations; the orientation of the acetyl carbonyl group close to the anomeric position was found to contribute significantly to the directing of the anomerization reaction. By exploiting this reaction, oligoaminoglycosides with multiple 1,2‐cis glycosidic bonds were generated from 1,2‐trans glycosides in a one‐step process.     

Gold(I)‐Catalyzed Diastereo‐ and Enantioselective Synthesis of Polysubstituted Pyrrolo[3,4‐d][1,2]oxazines

A gold(I)‐catalyzed highly diastereo‐ and enantioselective intermolecular cycloaddition of oxime ethers with nitrones under mild conditions was developed, which provides an facile access to optically pure highly substituted pyrrolo[3,4‐d][1,2]oxazines. The salient features of this reaction include general substrate scope, high efficiency, high enantioselectivity, readily available starting materials, and the use of commercially available ligand.