Novel Stereoselective Synthesis of Densely Functionalized 2H‐Indeno[2,1‐b]furans

An easy access to densely functionalized 2H‐indeno[2,1‐b]furans is presented starting from triphenylphosphine, dialkyl acetylenedicarboxylates, alcohols (propargyl alcohol, 2,2,2‐trichloroethanol, and methanol), and ninhydrin. The stereochemistry of dimethyl 8‐oxo‐8a‐(2,2,2‐trichloroethoxy)‐8,8a‐dihydro‐2H‐indeno[2,1‐b]furan‐2,3‐dicarboxylate was established by single‐crystal X‐ray structure determination. The reaction is completely stereoselective.     

Multicomponent Transformation of Isoindoline‐1,3‐diimine (=1H‐Isoindole‐1,3(2H)‐diimine), Acetylenic Esters,and Triphenylphosphine to Novel Dihydropyrimido[2,1‐a]isoindole Derivatives

The three‐component reaction of the zwitterions generated from dialkyl acetylenedicarboxylates (=dialkyl but‐2‐ynedioates and triphenylphosphine (Ph₃P) with isoindoline‐1,3‐diimine (=1H‐isoindole‐1,3(2H)‐diimine) is described (Scheme 1). This reaction affords the corresponding special type of substituted dihydropyrimido[2,1‐a]isoindole derivatives in good yields without using any catalyst and activation (Table).     

Dipotassium Hydrogen Phosphate Powder Catalyzed Synthesis of Alkyl 2-(2-Alkoxy-2-oxoethyl)dinaphtho[2,1-d:1,2-f][1,3]-dioxepin-2-Carboxylates from Stabilized Phosphorus Ylides in Solvent-Free Conditions

The protonation of the highly reactive 1:1 intermediates, produced in the reaction of triphenylphosphine and dialkyl acetylenedicarboxylates, by 1,1-binaphthyl-2,2′-diol leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction to produce the corresponding stabilized phosphonium ylides. Dipotassium hydrogen phosphate powder was found to catalyze the conversion of the stabilized phosphonium ylides to alkyl 2-(2-alkoxy-2-oxoethyl)dinaphtho[2,1-d:1,2-f][1,3]-dioxepin-2-carboxylates under solvent-free conditions using microwave (0.6 KW, 3 min) and thermal (100°C, 60 min) conditions.     

A Facile One‐Pot Synthesis of Functionalized 1,5‐Dihydro‐2H‐[1]benzopyrano[2,3‐b]pyridin‐5‐ones

The highly reactive 1 : 1 intermediate generated in the reaction between dialkyl acetylenedicarboxylate (=but‐2‐ynedioic acid dialkyl ester) 4 and triphenylphosphine was trapped by 2‐amino‐4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehydes 5 to yield highly functionalized dialkyl‐1,5‐dihydro‐5‐oxo‐1‐phenyl‐2H‐[1]benzopyrano[2,3‐b]pyridine‐2,3‐dicarboxylates in high yield.     

A New Four‐Component Reaction for the Synthesis of Spiro[4H‐indeno[1,2‐b]pyridine‐4,3′‐[3H]indoles]

A new four‐component synthesis of spiro[4H‐indeno[1,2‐b]pyridine‐4,3′‐[3H]indoles] and spiro[acenaphthylene‐1(2H),4′‐[4H‐indeno[1,2‐b]pyridines] by the reaction of indane‐1,3‐dione, 1,3‐dicarbonyl compounds, isatins (=1H‐indole‐2,3‐diones) or acenaphthylene‐1,2‐dione, and AcONH₄ in refluxing toluene in the presence of a catalytic amount of pyridine is reported.     

One‐Pot,Four‐Component Synthesis of Novel Spiro[indeno[2,1‐b]quinoxaline‐11,4′‐pyran]‐2′‐amines

A one‐pot, four‐component reaction for the efficient synthesis of novel spiro[indeno[2,1‐b]quinoxaline‐11,4′‐pyran]‐2′‐amines by using InCl₃ is described. The syntheses are achieved by reacting ninhydrin with 1,2‐diaminobenzenes to give indenoquinoxalines, which are trapped in situ by alkyl malonates and various α‐methylencarbonyl compounds through cyclization, providing multifunctionalized spiro‐substituted indeno[2,1‐b]quinoxaline‐11,4′‐pyran‐2′‐amines.     

Pd‐Catalyzed Cyclocarbonylation of 2‐(2‐Bromoaryl)indoles with CO as a C1 Source: Selective Access to 6 H‐Isoindolo[2,1‐a]indol‐6‐ones and Indeno[1,2‐b]indol‐10(5 H)‐ones

A highly efficient and regioselective synthetic route to 6 H‐isoindolo[2,1‐a]indol‐6‐ones and indeno[1,2‐b]indol‐10(5 H)‐ones through the Pd‐catalyzed cyclocarbonylation of 2‐(2‐bromoaryl)indoles under atmospheric CO pressure has been achieved. Notably, the regioselectivity of the reaction was exclusively dependent on the structural characteristics of the indole substrates. With N‐unsubstituted indoles as the starting materials, the reaction afforded 6H‐isoindolo[2,1‐a]indol‐6‐ones in good‐to‐excellent yields. On the other hand, with N‐substituted indoles as the substrates, the reaction gave indeno[1,2‐b]indol‐10(5 H)‐ones in a highly regioselective manner.     

A Novel Route to 1‐Substituted 3‐(Dialkylamino)‐9‐oxo‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitriles

Heptalenecarbaldehydes 1 / 1′ as well as aromatic aldehydes react with 3‐(dicyanomethylidene)‐indan‐1‐one in boiling EtOH and in the presence of secondary amines to yield 3‐(dialkylamino)‐1,2‐dihydro‐9‐oxo‐9H‐indeno[2,1‐c]pyridine‐4‐carbonitriles (Schemes 2 and 4, and Fig. 1). The 1,2‐dihydro forms can be dehydrogenated easily with KMnO₄ in acetone at 0° (Scheme 3) or chloranil (=2,3,5,6‐tetrachlorocyclohexa‐2,5‐diene‐1,4‐dione) in a ‘one‐pot’ reaction in dioxane at ambient temperature (Table 1). The structures of the indeno[2,1‐c]pyridine‐4‐carbonitriles 5′ and 6a have been verified by X‐ray crystal‐structure analyses (Fig. 2 and 4). The inherent merocyanine system of the dihydro forms results in a broad absorption band in the range of 515–530 nm in their UV/VIS spectra (Table 2 and Fig. 3). The dehydrogenated compounds 5, 5′ , and 7a – 7f exhibit their longest‐wavelength absorption maximum at ca. 380 nm (Table 2). In contrast to 5 and 5′, 7a – 7f in solution exhibit a blue‐green fluorescence with emission bands at around 460 and 480 nm (Table 4 and Fig. 5).     

A Facile and Expeditious Microwave‐Assisted Synthesis of Furo[3,4‐b]indeno[2,1‐f]quinolin‐1‐one Derivatives via Multicomponent Reaction

A series of furo[3,4‐b]indeno[2,1‐f]quinolin‐1‐one derivatives were synthesized by the condensation of an aromatic aldehyde with tetronic acid and 9H‐fluoren‐2‐amine in solvent of glacial acetic acid under microwave irradiation. This procedure offers several advantages including operational simplicity, clean reaction, and increased safety for small‐scale high‐speed synthesis.     

一种以水相中微波促进下的多组分反应合成具有重要生物意义的茚并[2,1-e]吡唑并[5,4-b]吡啶的绿色方法

在无催化剂的条件下,以醛、3-甲基-1-苯基-1H-吡唑-5-胺和1,3-茚二酮为原料,通过水相中微波促进下的多组分反应,成功地实现了具有重要生物意义的茚并[2,1-e]吡唑并[5,4-b]吡啶的绿色合成。这种方法具有环境友好、反应时间短、产率高、价廉、操作简单以及广泛的适用范围等显著优点。     

Synthesis of Dialkyl 2‐(Alkylamino)‐4,9‐dihydro‐9‐oxocyclohepta[b]pyran‐3,4‐dicarboxylates

Dialkyl 2‐(alkylamino)‐4,9‐dihydro‐9‐oxocyclohepta[b]pyran‐3,4‐dicarboxylates are prepared in a one‐pot three‐component reaction of alkyl isocyanide, dialkyl acetylenedicarboxylate, and α‐tropolone (=2‐hydroxycyclohepta‐2,4,6‐trienone). The reaction proceeds smoothly at room temperature and under neutral conditions to afford tropolone derivatives in high yield.     

Synthesis of Imidazo[2,1‐b][2H‐1,3,4]thiadiazines and 1,2,4‐Triazolo[3,4‐b][2H‐1,3,4]thiadiazines

Imidazo[2,1‐b][2H‐1,3,4]thiadiazines were prepared by cyclization of 2‐amino‐5‐(4‐chlorophenyl)‐6H‐1,3,4‐thiadiazine with α‐haloketones. 1,2,4‐Triazolo[3,4‐b][2H‐1,3,4]thiadiazines were prepared by cyclization of 4‐amino‐5‐sulfanyl‐l,2,4‐triazoles with phenacyl bromides.     

Diversity‐Oriented Synthesis of Novel 2′‐Aminospiro[11H‐indeno[1,2‐b]quinoxaline‐11,4′‐[4H]pyran] Derivatives via a One‐Pot Four‐Component Reaction

A sequential one‐pot four‐component reaction for the efficient synthesis of novel 2′‐aminospiro[11H‐indeno[1,2‐b]quinoxaline‐11,4′‐[4H]pyran] derivatives 5 in the presence of AcONH₄ as a neutral, inexpensive, and dually activating catalyst is described (Scheme 1). The syntheses are achieved by reacting ninhydrin ( 1 ) with benzene‐1,2‐diamines 2 to give indenoquinoxalines, which are trapped in situ by malono derivatives 2 and various α‐methylenecarbonyl compounds 4 through cyclization, providing the multifunctionalized 2′‐aminospiro[11H‐indeno[1,2‐b]quinoxaline‐11,4′‐[4H]pyran] analogs 5 . This chemistry provides an efficient and promising synthetic way of proceeding for the diversity‐oriented construction of the spiro[indenoquinoxalino‐pyran] skeleton.     

Different patterns of supramolecular assembly in constitutionally similar 6‐arylimidazo[2,1‐b][1,3,4]thiadiazoles

Four imidazo[2,1‐b][1,3,4]thiadiazoles containing a simply‐substituted 6‐aryl group have been synthesized by reaction of 2‐amino‐1,3,4‐thiadiazoles with bromoacetylarenes using microwave irradiation and brief reaction times. 6‐(2‐Chlorophenyl)imidazo[2,1‐b][1,3,4]thiadiazole, C₁₀H₆ClN₃S, (I), 6‐(2‐chlorophenyl)‐2‐methylimidazo[2,1‐b][1,3,4]thiadiazole, C₁₁H₈ClN₃S, (II), 6‐(3,4‐dichlorophenyl)imidazo[2,1‐b][1,3,4]thiadiazole, C₁₀H₅Cl₂N₃S, (III), and 6‐(4‐fluoro‐3‐methoxyphenyl)‐2‐methylimidazo[2,1‐b][1,3,4]thiadiazole, C₁₂H₁₀FN₃OS, (IV), crystallize with Z′ values of 2, 1, 1 and 2 respectively. The molecular skeletons are all nearly planar and the dihedral angles between the imidazole and aryl rings are 1.51 (8) and 7.28 (8)° in (I), 9.65 (7)° in (II), 10.44 (8)° in (III), and 1.05 (8) and 7.21 (8)° in (IV). The molecules in (I) are linked by three independent C—H...N hydrogen bonds to form ribbons containing alternating R₂²(8) and R₄⁴(18) rings, and these ribbons are linked into a three‐dimensional array by three independent π‐stacking interactions. Both (II) and (III) contain centrosymmetric dimers formed by π‐stacking interactions but hydrogen bonds are absent, and the molecules of (IV) are linked into centrosymmetric R₂²(8) dimers by C—H...N hydrogen bonds. Comparisons are made with a number of related compounds.     

Convenient Synthesis of Spiro[benzo[d]pyrrolo[2,1‐b]thiazole‐3,2′‐indenes] Derivatives via Three‐Component Reaction

The three‐component reaction of N‐phenacylbenzothiazolium bromides, aromatic aldehydes and indane‐1,3‐dione in ethanol at room temperature in the presence of triethylamine as base afforded functionalized spiro[benzo[d]pyrrolo[2,1‐b]thiazole‐3,2′‐indenes] in good yields and with high diastereoselectivity. The ¹H NMR data and single crystal structure clearly indicated that the obtained spiro compounds predominately have one diastereoisomer.     

Synthesis of New Functionalized Heterocyclic [4,3,3] Propellanes via Three‐component Reaction Based on Ninhydrin–Phenol Adducts

Three‐component reaction between ninhydrin–phenol adducts, dialkyl acetylenedicarboxylates, and triphenylphosphine was investigated. Utilizing this protocol, dialkyl 10‐oxo‐10H‐4b,9b‐(epoxyethanooxy)indeno[1,2‐b]benzofuran‐12,13‐dicarboxylates as functionalized heterocyclic [4,3,3] propellanes was synthesized in 6‐endo‐trig cyclization mode. 8‐hydroxyquinoline showed serendipitous reactivity and produced para substituted adduct in the reaction with ninhydrin in acetic acid media and hence produced dialkyl 8a‐(4‐(alkoxycarbonyl)‐2‐oxo‐2H‐pyrano[3,2‐h]quinolin‐6‐yl)‐8‐oxo‐8,8a‐dihydro‐2H‐indeno[2,1‐b]furan‐2,3‐dicarboxylate in the reaction with dialkyl acetylenedicarboxylates and PPh₃.     

An Efficient One‐Pot Synthesis of Substituted 1H‐Naphtho[2,1‐b]pyrans and 4H‐1‐Benzopyrans (=Chromenes) under Solvent‐Free Microwave‐Irradiation Conditions

A facile heterogeneous synthesis of 3‐amino‐1‐aryl‐1H‐naphtho[2,1‐b]pyran and 2‐amino‐4‐aryl‐4H‐1‐benzopyran derivatives 3 and 5 , respectively, was carried out efficiently by one‐pot three‐component coupling of an aromatic aldehyde 1 , an active methylene compound 2 , and naphthalen‐2‐ol or a phenol 4 in the presence of 5‐Å molecular sieves under solvent‐free microwave‐irradiation conditions (Scheme 1 and 2, Tables 1 and 2). The catalyst was recovered and recycled (Table 3).     

Reaction of cyclic imidates with α,β‐unsaturated esters: Synthesis of new pyrrolo[2,1‐b]‐1,3‐oxazine and pyrido[2,1‐b]‐1,3‐oxazine derivatives

The cycloaddition reaction of cyclic imidates, 2‐benzyl‐5,6‐dihydro‐4H‐1,3‐oxazines 1a , 1b , 1c , 1d , 1e , 1f , with dimethyl acetylenedicarboxylate 2 , trimethyl ethylenetricarboxylate 4 , or dimethyl 2‐(methoxymethylene)malonate 6 afforded new fused heterocyclic compounds, such as methyl (6‐oxo‐3,4‐dihydro‐2H‐pyrrolo[2,1‐b]‐1,3‐oxazin‐7‐ylidene)acetates 3a , 3b , 3c , 3d , 3e , 3f (71–79%), dimethyl 2‐(6‐oxo‐3,4,6,7‐tetrahydro‐2H‐pyrrolo[2,1‐b]‐1,3‐oxazin‐7‐yl)malonates 5b , 5c , 5d , 5e , 5f (43–71%), or methyl 6‐oxo‐3,4‐dihydro‐2H,6H‐pyrido[2,1‐b]‐1,3‐oxazine‐7‐carboxylates 7a , 7b , 7c , 7d , 7e , 7f (32–59%), respectively. In these reactions, 1a , 1b , 1c , 1d , 1e , 1f (cyclic imidates, iminoethers) functioned as their N,C‐tautomers (enaminoethers) 2 to α,β‐unsaturated esters 2 , 4, and 6 to give annulation products 3 , 5 , and 7 following to the elimination of methanol, respectively. J. Heterocyclic Chem., (2011).     

Synthesis of 2H‐Indazolo[2,1‐b]Phthalazine‐1,6,11(13H)‐Trione Derivatives Using Wet Cyanuric Chloride under Solvent‐Free Condition

A simple and facile synthesis of 2H‐indazolo[2,1‐b]phthalazine‐1,6,11(13H)‐trione derivatives has been accomplished by a three‐component condensation reaction of dimedone, aromatic aldehydes and phthalhydrazide under solvent‐free conditions in the presence of wet cyanuric chloride as a catalyst.     

A Diastereoselective Synthesis of Functionalized Tetrahydroindeno[2′,1′,3,4]pyrido[2,1‐a]isoquinolines

An effective route to alkyl 9a‐(2,3‐dihydro‐1,3‐dioxo‐1H‐inden‐2‐yl)‐9a,14,14a,14b‐tetrahydro‐14‐oxoindeno[2′,1′:3,4]pyrido[2,1‐a]isoquinoline‐9‐carboxylates via a diastereoselective one‐pot four‐component reaction of isoquinoline and alkyl prop‐2‐ynoates with two equivalents of indane‐1,3‐dione, in aqueous MeOH at room temperature, is described.