A novel one-pot and efficient procedure for the synthesis of 3H-spiro[isobenzofuran-1,6′-pyrrolo[2,3-d]pyrimidine]-2′,3,4′,5′-tetraones

A novel and practical one-pot procedure is described for the preparation of several new of 3H-spiro[isobenzofuran-1,6′-pyrrolo[2,3-d]pyrimidine]-2′,3,4′,5′-tetraones based on the addition reaction of ninhydrin and 6-aminouracils followed by oxidative cleavage of their corresponding dihydroxyindenopyrrolopyrimidines.     

A regioselective three-component reaction for synthesis of novel 1′H-spiro[isoindoline-1,2′-quinazoline]-3,4′(3′H)-dione derivatives

A ring opening and regioselective three-component reaction of isatoic anhydride, isatins, and aromatic or aliphatic primary amines in the presence of catalytic amount of KAl(SO₄)₂·12H₂O (alum) to yield a novel series of 1′H-spiro[isoindoline-1,2′-quinazoline]-3,4′(3′H)-dione is described.     

One-pot synthesis of novel spiro 2,3,7,8-tetrahydro-benzo[1,2-b:5,4-b′]dipyran-4,6-dione and 2,3,8,9-tetrahydro-benzo[1,2-b:4,3-b′]dipyran-4,10-dione derivatives

An efficient synthesis of novel spiro 2,3,7,8-tetrahydro-benzo[1,2-b:5,4-b′]dipyran-4,6-dione and 2,3,8,9-tetrahydro-benzo[1,2-b:4,3-b′]dipyran-4,10-dione derivatives in high yields under microwave irradiation is described. The reaction was also studied under conventional heating conditions.     

Multicomponent one-pot solvent-free synthesis of functionalized unsymmetrical dihydro-1H-indeno[1,2-b]pyridines

A simple and efficient synthesis of 4-aryl-4,5-dihydro-1H-indeno[1,2-b]pyridine derivatives has been achieved via a four-component cyclocondensation of 1,3-indanedione, aromatic aldehydes, β-ketoesters and ammonium acetate in one-pot in the absence of catalyst and solvent at room temperature on grinding. The present approach offers several advantages such as shorter reaction times, higher yields, low cost, simple work-up and easy purification.     

Solvent-free sonochemical one-pot three-component synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11-triones and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones

A rapid and efficient one-pot three-component protocol for the synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11-triones 4 and 1H-pyrazolo[1,2-b]phthalazine-5,10-diones 6 has been developed by domino coupling of phthalhydrazide, 1,3-diketones, and aldehydes under solvent-free conditions at 80 °C as well as under solvent-free ultrasound irradiation at room temperature promoted by (S)-camphorsulfonic acid.     

Facile synthesis of 3H,3′H-spiro[benzofuran-2,1′-isoindole]-3,3′-diones using monobromomalononitrile (MBM) as an efficient organo-brominating agent

An efficient methodology for the synthesis of 3H,3′H-spiro[benzofuran-2,1′-isoindole]-3,3′-diones has been developed where monobromomalononitrile (MBM) has been employed as a non-hazardous brominating agent under ambient reaction condition. The intrinsic advantages of the methodology are the utilization of simple and easily available starting materials and non-toxic reagents, operational simplicity, and good yields of the products with high atom-economy.     

Synthesis of pyrrolo[3,4-b]pyrroles and perhydrothiazolo[3′,4′-2,3]pyrrolo[4,5-c]pyrroles

The 1,3-dipolar cycloaddition reactions of various N-tethered alkenyl aldehydes with some cyclic and acyclic amino acids have been studied. Some key sulfonamides having strategically positioned aldehyde and olefinic tether have been synthesized and effectively subjected to intramolecular azomethine ylide cycloaddition reaction resulting in a series of pyrrolo[3,4-b]pyrrole and its N-1-C-2 derivatives, and a series of novel heterotricyclic compounds, perhydrothiazolo[3′,4′-2,3]pyrrolo[4,5-c]pyrroles, in good yields. The intramolecular cycloaddition reaction was found to be highly stereoselective to form only cis-fused cycloadducts in all cases.     

Cascade assembly of N,N′-dialkylbarbituric acids and aldehydes: a simple and efficient one-pot approach to the substituted 1,5-dihydro-2H,2′H-spiro(furo[2,3-d]pyrimidine-6,5′-pyrimidine)-2,2′,4,4′,6′(1′H,3H,3′H)-pentone framework

Cascade assembly of N,N′-dialkylbarbituric acids and aldehydes in the presence of bromine leads to the selective and efficient formation of substituted 1,5-dihydro-2H,2′H-spiro(furo[2,3-d]pyrimidine-6,5′-pyrimidine)-2,2′,4,4′,6′-(1′H,3H,3′H)-pentones in 70-88% yields via a complex cascade process. Spirobarbiturates containing the furo[2,3-d]pyrimidine framework are a class of compounds with interesting pharmacological and physiological activity.     

Asymmetric route to spirotetracyclic (1S)-5′,11′-dihydro-3H-spiro[cyclopentane-1,10′-dibenzo[a,d]cyclohepten]-3-one derivatives

A new synthetic pathway to the final compound 1-[(1S)-5’,11’-dihydrospiro[cyclopentane-1,10’-dibenzo[a,d]cyclohepten]-3-yl]-3-azetidinecarboxylic acid (1) was set up. The two preparative chiral HPLC separations needed in the first route were successfully avoided and replaced by two diastereomeric crystallizations of intermediate compounds 5 and 10.     

One-pot, three-component route to 2H-indazolo[2,1-b]phthalazine-triones

2H-Indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivatives were synthesized in a simple and efficient method from the three-component condensation reaction of phthalhydrazide, dimedone, and aromatic aldehydes under solvent-free conditions in excellent yields and short reaction times.     

Novel synthesis and characterisation of 3,3-dimethyl-5′-(2-benzothiazolyl)-spironaphth(indoline-2,3′-[3H]naphth[2,1-b] [1,4]oxazine) derivatives

Novel modified spirooxazines (SOs) with additional chelating groups were synthesised and the crystal structure of one of these was determined. UV-vis spectroscopic characterization of the photoisomerization of the SO derivatives shows that the photochromic behaviour is altered with Zn²⁺ coordination. In particular, addition of a group as in carboxylic acid 5 to the indole section of the SO increases the lifetime of the merocyanine Zn ²⁺ complex by 20-fold compared to the methylated indole 6.     

Indium(III)chloride catalyzed synthesis of novel 1H-pyrazolo[1,2-b]phthalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-diones under solvent-free condition

An efficient, inexpensive and environmentally friendly synthesis of novel 3-amino-2-benzoyl-1-aryl-1H-pyrazolo[1,2-b]phthalazine-5,10-dione and 3-amino-2-benzoyl-1-aryl-1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives has been developed via one-pot three-component reaction of phthalhydrazide or maleic hydrazide, aldehydes and arylacetonitrile in the presence of catalytic amount of InCl₃ as a Lewis acid catalyst under solvent-free conditions. The most important features of the present protocol are mild reaction conditions, short reaction times, high yields, and a wide range of functional group tolerance.     

Silica sulfuric acid: an efficient reusable heterogeneous solid support for the synthesis of 3H,3′H-spiro[benzofuran-2,1′isobenzofuran]-3,3′-diones under solvent-free condition

A highly efficient protocol for the library synthesis of biologically important 3H,3′H-spiro[benzofuran-2,1′isobenzofuran]-3,3′-diones has been developed by employing silica sulfuric acid (SSA) as solid acid support under solvent-free condition. The dual characteristics of SSA, as an activating agent as well as oxidizing agent, have been well exposed in these syntheses. The intrinsic advantages of the methodology are the use of solvent-free reaction condition without using any toxic reagents or metal catalyst, operational simplicity, recyclability of the solid support, good availability of the starting materials, and excellent yields which make the method attractive, economic, and ‘benign by design’.     

A simple route for the synthesis of 3,3,3′,3′-tetramethyl-2,3,3′,4′-tetrahydro-1H,1′H-[4,9′-bixanthene]-1,1′(2′H,9′H)-dione and its derivatives catalyzed by Mn and other transition metal cations

A simple and efficient unusual coupling reaction of 9-(2-hydroxy-4,4-dimethyl-6-oxocyclohex-1-en-1-yl)-3,3-dimethyl-2,3,4,9-tetrahydro-1H-xanthen-1-one and its derivatives was accomplished in the presence of Mn²⁺, Cu²⁺, Cd²⁺, Hg²⁺, Fe³, or La³⁺. The structure elucidation was accomplished by IR, ¹H NMR, ¹³C NMR, X-ray crystallography, UV-Visible and elemental analysis. A reaction mechanism is proposed.     

First synthesis of pyrrolo[1,2:1′,2′]azepino[5,6-b]indole derivatives

A new family of pyrrolo[1,2:1′,2′]azepino[5,6-b]indole derivatives 8,15 related to anthramycin skeleton was prepared in good yield from indole-2-carboxylic acid and β-aminoesters 4 through intramolecular cyclisation.     

Photo-induced aromatic assembly of benzocycloalka[1,2-b] furan and spiro[furan-2(3H),1′-benzocycloalkane] derivatives

The photo-induced benzannulation of benzocycloalka[1,2-b]furans produced hydrohelicene-type compounds in good yields. A similar photoreaction of the spiro[furan-2(3H),1′-benzocycloalkane]s afforded dihydrophenalene derivatives in moderate yields. Benzo[kl]xanthene was also formed by a similar photoreaction of spiro[furan-2(3H),9′-xanthene]. The reaction pathway was elucidated by the ¹H NMR spectrum of the reaction mixture and the alternative synthesis of the intermediate.     

A novel construction of quino-fused tropone skeleton: first synthesis of 12H-benzo[4,5]cyclohepta[1,2-b]quinolin-12-one derivatives

In the present investigation, the incorporation of both quinoline moiety and tropone ring in a molecule frame work in fused form leading to a series of structurally novel and biologically intriguing quinoline/tropone hybrids 12H-benzo[4,5]cyclohepta[1,2-b]quinolin-12-one derivatives has been first achieved through a simple, and economical two-step procedure, involving the one-pot synthesis of (E)-2-(arylvinyl)quinoline-3-carboxylic acids followed by intramolecular Friedel–Crafts acylation reaction using polyphosphoric acid (PPA).     

Synthesis of tetrahydropyrido- and pyrido-[1′,2′:1,2]imidazo[4,5-b]pyrazine derivatives

Reactions of tetrafluoropyridazine with iminopiperidine and 2-aminopiccoline gave novel tetrahydropyrido- and pyrido-[1′,2′:1,2]imidazo[4,5-b]pyrazine heterocyclic frameworks respectively in high yields.     

Facile synthesis of 1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives by a one-pot, three-component reactions

Protonation of the highly reactive 1:1 intermediate produced in the reaction between alkyl or aryl isocyanides and electron-deficient acetylenic esters with 3,6-dihydroxypyridazine, leads to a vinylisonitrilium cation, which undergoes an addition reaction with the conjugate base of the 3,6-dihydroxypyridazine to produce dialkyl 3-(alkyl or arylamino)-5,8-dioxo-5,8-dihydro-1H-pyrazolo[1,2-a]pyridazine-1,2-dicarboxylates in good yields at room temperature.     

Improved synthesis of N-alkyl substituted dithieno[3,2-b:2′,3′-d]pyrroles

A new, convergent and improved synthetic method to prepare N-alkyl substituted dithienopyrroles is described. The procedure consists of a Pd-catalyzed amination of 3,3′-dibromo-2,2′-bithiophene. The reaction conditions were optimized, which makes this method applicable to prepare these molecules easily in high yields and on a large scale.