Ethyl 6‐acetylamino‐6,7‐dihydro‐5H‐dibenzo[a,c]cycloheptene‐6‐carboxylate

The title compound, C₂₀H₂₁NO₃, is a derivative of Aib (α‐­aminoisobutyric acid) and is cyclized at the C^α position by bi­phenyl rings. The seven‐membered ring possesses C2 symmetry. The C^α cyclization causes the backbone to assume a helical conformation in the crystal structure. The packing of the mol­ecules is stabilized by intermolecular C—H?O, C—H?π and N—H?O hydrogen bonds.     

NMR analysis of 6‐(2′,3′‐dihydro‐1′H‐inden‐1′‐yl)‐1H‐indene

¹H, ¹³C and two‐dimensional NMR analyses were applied to determine the NMR parameters of 6‐(2′,3′‐dihydro‐1′H‐inden‐1′‐yl)‐1H‐indene. The measurements were accomplished with 0.5 mg of the substance, this quantity being sufficient to determine the chemical shifts of all the H and C atoms, and also the appropriate coupling constants and to give the complete NMR resonance assignments of the molecule. The predicted patterns of the four different H atoms of the methylene groups of the indane structural element coincided completely with the complex patterns in the NMR spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Dicyano(7‐methyl‐6‐oxo‐6H‐dibenzo[b,d]pyran‐9‐yl)methanide Salts via a Multicomponent Reaction

Dialkylammonium dicyano(7‐methyl‐6‐oxo‐6H‐dibenzo[b,d]pyran‐9‐yl)methanides 4a – 4j are obtained in good yields via a simple reaction between 3‐acetylcoumarins (=3‐acetyl‐2H‐1‐benzopyran‐2‐ones) 1 and malononitrile ( 2 ) in EtOH (Table 1). In this reaction, a charge‐separated zwitterionic salt is formed.     

5‐Acetyl‐2‐amino‐6‐methyl‐4‐(3‐nitrophenyl)‐4H‐pyran‐3‐carbonitrile and 2‐amino‐5‐ethoxycarbonyl‐6‐methyl‐4‐(3‐nitrophenyl)‐4H‐pyrano‐3‐carbonitrile

The structures of the title compounds, C₁₅H₁₃N₃O₄, (I), and C₁₆H₁₅N₃O₅ [IUPAC name: ethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(3‐nitro­phenyl)‐4H‐pyrano‐3‐carboxyl­ate], (II), are very similar, with the heterocyclic rings adopting boat conformations. The pseudo‐axial m‐nitro­phenyl substituents are rotated by 84.0 (1) and 98.7 (1)° in (I) and (II), respectively, with respect to the four coplanar atoms of the boat. The dihedral angles between the phenyl rings and nitro groups are 12.1 (2) and 8.4 (2)° in (I) and (II), respectively. The two compounds have similar patterns of intermolecular N—H?O and N—H?N hydrogen bonding, which link mol­ecules into infinite tapes along b .     

An Efficient and Facile Multicomponent Reaction for the Synthesis of 5′,6′‐dihydro‐6′‐hydroxy‐6′‐(trifluoromethyl)‐1′H‐spiro[indoline‐3,4′‐pyrimidine]‐2,2′(3′H)‐dione Derivatives under Solvent‐Free Conditions

The reactions of isatins, urea, and different diketones under solvent‐free conditions have been developed for the preparation of novel spiroheterocycles. It was found that these reactions could be given higher yields and required shorter time compared with commonly used volatile organic solvent conditions. In this synthesis, the important group trifluoromethyl was introduced into the structure of the products. The pure products could be obtained only through removing TsOH, isatins, and urea from hot water. At same time, diketone was eliminated through a small amount of EtOH. Other advantages of this method are simple setup, mild conditions, and minimal environment impact.     

Synthesis and reactivity of 6‐methyl‐4H‐furo[3,2c]pyran‐3,4‐dione

An efficient synthesis of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one by bromination of dehydroacetic acid in glacial acetic acid is described. Novel 4‐hydroxy‐6‐methyl‐3‐(2‐substituted‐thiazol‐4‐yl)‐2H‐pyran‐2‐ones have been prepared from the reaction of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with thioamides, thiourea, and diphenylthiocarbazone. The condensation reaction of 6‐methyl‐4H‐furo[3,2c]pyran‐3,4‐dione, obtained from the reaction of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with aliphatic amines, with benzaldehydes and acetophenones led to novel 2‐arylidene‐6‐methyl‐2H‐furo[3,2‐c]pyran‐3,4‐diones and 6‐(2‐arylprop‐1‐enyl)‐2H‐furo[3,2‐c]pyran‐3,4‐diones. The structure of all compounds was established by elemental analysis, IR, NMR, and mass spectra. J. Heterocyclic Chem., 2011.     

Three sterically hindered 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate derivatives

In the title compounds, 2‐methoxyethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₁H₂₀N₂O₄, (II), isopropyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₁H₂₀N₂O₃, (III), and ethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(1‐naphthyl)‐4H‐pyran‐3‐carboxylate, C₂₀H₁₈N₂O₃, (IV), the heterocyclic pyran ring adopts a flattened boat conformation. In (II) and (III), the carbonyl group and a double bond of the heterocyclic ring are mutually anti, but in (IV) they are mutually syn. The ester O atoms in (II) and (III) and the carbonyl O atom in (IV) participate in intramolecular C—H...O contacts to form six‐membered rings. The dihedral angles between the naphthalene substituent and the closest four atoms of the heterocyclic ring are 73.3 (1), 71.0 (1) and 74.3 (1)° for (II)–(IV), respectively. In all three structures, only one H atom of the NH₂ group takes part in N—H...O [in (II) and (III)] or N—H...N [in (IV)] intermolecular hydrogen bonds, and chains [in (II) and (III)] or dimers [in (IV)] are formed. In (II), weak intermolecular C—H...O and C—H...N hydrogen bonds, and in (III) intermolecular C—H...O hydrogen bonds link the chains into ladders along the a axis.     

New synthesis and reactivity of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with binucleophilic amines

3‐(Bromoacetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one was synthesized by the reaction of dehydroacetic acid (DHAA) with bromine in glacial acetic acid. Novel heterocyclic products were synthesized from the reaction of bromo‐DHAA with alkanediamines, phenylhydrazines, ortho‐phenylenediamines, and ortho‐aminobenzenethiol. The obtained new products 3‐(2‐N‐substituted‐acetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐ones, 4‐hydroxy‐3‐[1‐hydroxy‐2‐(2‐phenylhydrazinyl)vinyl]‐6‐methyl‐2H‐pyran‐2‐one, 1‐(2,4‐dinitrophenyl)‐7‐methyl‐2,3‐dihydro‐1H‐pyrano[4,3‐c]pyridazine‐4,5‐dione, 3‐(3,4‐dihydroquinoxalin‐2‐yl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one/3‐(3,4‐dihydroquinoxalin‐2‐yl)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione, 6‐methyl‐3‐(3,4‐dihydroquinoxalin‐2‐yl)‐2H‐pyran‐2,4(3H)‐dione, and (E)‐3‐(2H‐benzo[b][1,4]thiazin‐3(4H)‐ylidene)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione were fully characterized by IR, ¹H and ¹³C NMR, and mass spectra. J. Heterocyclic Chem., 2011.     

Molecular dynamics of 6‐methyl‐2‐phenyl‐2,3‐dihydro‐4H‐chromen‐4‐one and 6‐methyl‐2‐(4‐nitrophenyl)‐2,3‐dihydro‐4H‐chromen‐4‐one (flavanone) derivatives in a solution studied by NMR spectroscopy

Molecular dynamics of benzoxazepin, oxime, pyrazole, and thiosemicarbazone derivatives of some flavanones have been investigated in a solution using NMR. The results confirm the formation of different O–H···O, O–H···N, N···H–N type intramolecular hydrogen bonds in the pyrazole and oxime molecules. The rotational barrier energy and energy of intramolecular hydrogen bonds have been determined. Copyright © 2013 John Wiley & Sons, Ltd.     

(M)‐ and (P)‐8‐[(1S,2R)‐2‐hydroxy‐1‐methyl‐2‐phenylethyl]‐8‐methyl‐8,9‐dihydro‐7H‐dinaphth[2,1‐c:1′,2′‐e]azepinium bromide solvates

The title compounds are diastereoisomers with antipodean axial chirality. The M isomer crystallizes as a (1/3) acetone solvate, C₃₂H₃₀NO⁺·Br^?·3C₃H₆O, while the P isomer crystallizes as a (1/1) di­chloro­methane solvate, C₃₂H₃₀NO⁺·Br^?·CH₂Cl₂. In each structure, O—H?Br hydrogen bonds link the cations and anions to give ion pairs. The seven‐membered azepinium ring adopts the usual twisted‐boat conformation and its ring strain causes a slight curvature of the plane of each naphthyl ring.     

New approach to the synthesis of substituted 7H‐furo[3,2‐b]pyran‐7‐ones based on 5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one derivatives

A convenient approach to the synthesis of the previously unknown 7H‐furo[3,2‐b]pyran‐7‐ones based on the intramolecular cyclization of carbonyl derivatives of 5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one has been elaborated. Key intermediates in the synthesis of the target 7H‐furo[3,2‐b]pyran‐7‐ones are 3‐hydroxy‐6‐methyl‐2‐(2‐oxo‐2‐arylethyl)‐4H‐pyran‐4‐ones. They are formed as a result of multicomponent condensation of 5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one with arylglyoxals and 4‐methoxyaniline.     

4‐hydroxy‐6‐methyl‐3‐(5‐phenyl‐2E,4E‐pentadien‐1‐oyl)‐2H‐pyran‐2‐one: Synthesis and reactivity with amines

The synthesis and reactivity studies of 4‐hydroxy‐6‐methyl‐3‐(5‐phenyl‐2E,4E‐pentadien‐1‐oyl)‐2H‐pyran‐2‐one 2 with nucleophiles are reported. Reactions of 2 with hydrazine derivatives gave new pyrazole‐type com pounds while the reaction with ortho‐phenylenediamines yielded 1,5‐benzodiazepines. The reaction of 2 with ethylamine implies the 2H‐pyran‐2‐one ring opening and the formation of a strong conjugated compound 3.     

Microwave‐Assisted Direct Amidation of Ethyl 1‐Phenyl‐5‐hydroxy‐1H‐pyrazole‐4‐carboxylate

Microwave‐assisted treatment of ethyl 5‐hydroxy‐1‐phenyl‐1H‐pyrazole‐4‐carboxylate with excess primary aliphatic amines in 1‐propanol at 140°C and with excess pyrrolidine or piperidine in 2‐methoxyethanol at 180°C produced the corresponding carboxamides in good yields.     

Ethyl (6aRS,8RS,12bRS)‐6‐oxo‐8‐phenyl‐6a,7,8,12b‐tetra­hydro‐6H‐benzo­[b]naphtho­[1,2‐d]­pyran‐6a‐carboxylate

In the title compound, C₂₆H₂₂O₄, the pyran­one ring adopts a twisted boat conformation, while the cyclo­hexane ring is close to an envelope conformation. The dihedral angle between the mean planes of the coumarin and naphthalene systems is 78.8 (1)°. The attached phenyl ring is in an equatorial position with respect to the cyclo­hexane ring.     

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.     

5‐Acetyl‐2‐amino‐6‐methyl‐4‐phenyl‐4H‐pyran‐3‐carbonitrile and 2‐amino‐5‐benzoyl‐6‐methyl‐4‐phenyl‐4H‐pyran‐3‐carbonitrile acetonitrile solvate

The syntheses, X‐ray structural investigations and calculations of the conformational preferences of the carbonyl substituent with respect to the pyran ring have been carried out for the two title compounds, viz. C₁₅H₁₄N₂O₂, (II), and C₂₀H₁₆N₂O₂·C₂H₃N, (III), respectively. In both mol­ecules, the heterocyclic ring adopts a flattened boat conformation. In (II), the carbonyl group and a double bond of the heterocyclic ring are syn, but in (III) they are anti. The carbonyl group forms a short contact with a methyl group H atom in (II). The dihedral angles between the pseudo‐axial phenyl substituent and the flat part of the pyran ring are 92.7 (1) and 93.2 (1)° in (II) and (III), respectively. In the crystal structure of (II), inter­molecular N—H⋯N and N—H⋯O hydrogen bonds link the mol­ecules into a sheet along the (103) plane, while in (III), they link the mol­ecules into ribbons along the a axis.     

An Efficient Synthesis of 3‐(3‐benzyl‐2‐(phenylimino)‐2,3‐dihydrothiazol‐4‐yl)‐6‐methyl‐4‐(2‐oxo‐2‐phenylethoxy)‐3,4‐dihydro‐2H‐pyran‐2‐one Derivatives via Multi‐Component Approach

An easy, highly efficient and a new convenient one‐pot, two‐step approach to the synthesis of 3‐(3‐benzyl‐2‐(phenylimino)‐2,3‐dihydrothiazol‐4‐yl)‐6‐methyl‐4‐(2‐oxo‐2‐phenylethoxy)‐3,4‐dihydro‐2H‐pyran‐2‐one is described. These compounds were synthesized from 3‐(3‐benzyl‐2‐(phenylimino)‐2,3‐dihydrothiazol‐4‐yl)‐4‐hydroxy‐6‐methyl‐3,4‐dihydro‐2H‐pyran‐2‐one and α‐bromoketones in good yields. The compounds 4 were synthesized by a multi‐component reaction between 1 , 2 , and 3 and the prominent features of this protocol are mild reaction conditions, operation simplicity, and good to high yields of products.     

Regiospecific synthesis of 5‐(1H‐indol‐2‐yl)‐1‐ and 2‐methyl‐6,7‐dihydro‐2H‐indazole isomers

A regiospecific approach to each N‐methyl‐5‐(1H‐indol‐2‐yl)‐6,7‐dihydro‐2H‐indazole isomer is reported. The 1‐methyl isomer 1 was prepared from 5‐bromo‐1‐methyl‐6,7‐dihydro‐1H‐indazole 3 and indole‐2‐boronate 5 by palladium catalyzed Suzuki coupling. The 2‐methyl regioisomer 2 was synthesized via addition of lithium (1‐carboxylato‐1H‐indole‐2‐yl)lithium 6 with 2‐methyl‐2,4,6,7‐tetrahydro‐indazol‐5‐one 8 followed by acid catalyzed dehydration.     

2‐Chloro‐6‐(2‐furyl)‐9‐(4‐methoxybenzyl)‐9H‐purine

The title compound, C₁₇H₁₃ClN₄O₂, displays profound and selective activity against Mycobacterium tuberculosis. In the crystal structure, there are two independent molecules in the asymmetric unit. Intermolecular hydrogen bonding between a CH group of the purine ring and the O atom of the furan ring, and also π–π stacking in another direction, builds the three‐dimensional network.     

An Efficient Synthesis of N‐Substituted‐3‐aryl‐3‐(4‐hydroxy‐6‐methyl‐2‐oxo‐2H‐pyran‐3‐yl)propanamides by Four‐Component Reaction in Aqueous Medium

A mild and efficient synthesis of N‐substituted‐3‐aryl‐3‐(4‐hydroxy‐6‐methyl‐2‐oxo‐2H‐pyran‐3‐yl)propanamides via four‐component reaction of an aldehyde, amine, Meldrum's acid, and 4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one in the presence of benzyltriethylammonium chloride (TEBAC) in aqueous medium is described. This method has the advantages of accessible starting materials, good yields, mild reaction conditions, and begin environmentally friendly.