Cyclisation of 4-[2-Cyclofentenyl]-3-Hydroxy [1] Benzopypan-2-One

4-[2-cyclopentenyl]-3-hydroxy [1] bonzopyran-2-one(3) was cyclised to the bicyclie coumar in-1,3-ethano-2-bromo-1,2-dihydro-3H-pyrano [2,3-c] [1] benzopyran-5-one (6) by a sequence of reactions viz. acetylation of 3, addition of bromine to cyclopenteny double bond and treating the resulting acetyldibromo compound (5) with 4% alcoholic KOH, Cyclisation of compound (3) with mercuric acetate in methanol gave condensed furan derivative 7 which on reductive demercuration with zinc borohydride in dimethoxyethane gave the 1,3-propano-1,2-dihydrofuro [2,3-c] [1] benzopyran-4-one, 8. Cyclisation of compound 2 with come. H₂SO₄ furnished a mixture of bicyclic derivative 9 ad furo coumarin derivative 8.     

Regioselective Synthesis of 2H - Pyrano [3, 2-c] Benzopyran-5H-One and 3H-Pyrano [2, 3-c] Benzopyran-5H-ONE

The hitherto unreported title compounds were obtained in good yields by [3, 3] sigmatropic rearrangement of 4 - [2-propynyloxy] coumarin and 3 - [2-propyny-loxy] coumarin respectively.     

Photochemical Rearrangements of 6-Methoxymethylbicyclo[4.4.0]Dec-1-En-3-One and 6-Methoxymethylbicyclo[4.3.0]Non-1-En-3-One

The irradiation of the title compounds 6 and 12 in isooctane and benzene was investigated. The photochemical reactions took place sluggishly upon n→π^* excitation (λ > 300 nm) in deoxygenated solutions but more rapidly in the presence of air; deconjugation to yield β,γ-unsaturated ketones and lumiketone rearrangement were the main primary photochemical reactions. In contrast, intramolecular hydrogen abstraction by the C_α-carbon was the main reaction upon π→^* excitation (λ = 254 nm).     

Cyclization reactions of 3-hydrazino[1, 2, 4]triazino[5, 6-b]indole

The reaction of 3-hydrazino[1, 2, 4]triazino[5, 6-b]indole I with nitrous acid affords the azide III which could be cyclized with acetic anhydride to 10-acetyl-10H-tetrazolo[5′,1′:3, 4][1, 2, 4]triazino[5, 6-b]indole IIb . Cyclization reactions of I with acetic anhydride, ethyl chloroformate, carbon disulphide and aromatic aldehydes to the corresponding fused triazolo derivatives V–VIII are reported. On the other hand cyclization reactions of I with malononitrile, ethyl cyanoacetate, ethyl acetoacetate and acetylacetone to the corresponding condensed pyrazolino derivatives IX–XI are also reported. The reaction of I with α-dicarbonyl compounds to form mono and dihydrazones are reported. The structure of the compounds prepared and their cyclization mechanisms are reported.     

Studies in [3, 3] Sigmatropic Rearrangement: Regioselective Cyclization of 5-(Cyclohex-2-Enyl)-6-Hydroxy-1-Methylquinolin-2(1H)-One

Thermal [3,3] sigmatropic rearrangement of 6-cyclohex-2-enyloxy-1-methylquinolin-2(1H)-one (3) afforded 5-cyclohex-2-enyl-6-hydroxy-l-methyl-quinolin-2(1H)-one (4) in 86% yield. Compound 4 on treatment with pyridine hydrotribromide in CH₂Cl₂ gave exclusively non-bridged product 6 (85%) whereas compound 4 by a different route viz., acetylation followed by bromine addition and cyclization gave the bicyclic product 7 (80%). Compound 4 also furnished a bicyclic product 11 (80%) on treatment with cone. H₂SO₄.     

A New Synthesis of 2-(6-Methoxycarbonylhexyl)-Cyclopent-2-EN-1-One Using α-Silylallyl Sulphide

Acylation of the α-trimethylsilylallyl phenyl sulphide (2). by reaction with the acid chloride (3), catalyzed by aluminium chloride in CH₂Cl₂ at ?78°C, gave methyl 9-oxo-12-phenylthio-11-dodecene (4). Hydrolysis of (4) followed by aldol condensation gave 2-(6-methoxycarbonylhexyl)-cyclopent-2-en-1-one (6).     

TLC Separations of Some Closely Related 3-Hydroxy-6H-Benzofuro [2, 3-C] [1] Benzopyran-6 -Ones and Their Basic Ethers

Abstract

During the present study, the TLC separation of some closely related 3-hydroxy-6H-benzofuro [2, 3-C] [1] benzopyran-6-ones and their basic ethers have been carried out.     

The Rearrangement of 3, 4-Dihydro-2, 2-Dimethy-2H, 5H-Pyrano [2, 3-b][1] Benzopyran-5-Ones With DDQ

A novel rearrangement of 3, 4-dihydro-2, 2-dimethyl-2H, 5H-pyrano [2, 3-b] [1] benzopyran-5-ones (dihydropyranochromones) has been observed during the dehydrogenation with DDQ. The products obtained are found to be 2, 2-dimethyl-2H, 5H-pyrano [3, 2-c] [1] benzopyran-5-ones (pyranocoumarins).     

Synthesis of 2-R-3-Hydroxy[1,2,4]triazino[6,1-b]-quinazoline-4,10-diones

A preparation method was developed for [1,2,4]triazino[6,1-b]quinazoline-4,10-diones using isatoic anhydride, carboxylic acids hydrazides, ethyl oxalyl chloride, and hydroxylamine.     

Synthesis of Indolo[2,3-a]quinolizidine-3-One

The title compound 1 has been synthesised through the intermediacy of the salt 5 obtained by acid hydrolysis of the obtically active β-carboline derivative 10,11-cyclohexylidene-12β-hydroxy-13β-(l-tetrahydro-β-carbolinyl)tetrahydrofuran (4).     

可见光催化氮杂环丙烯与马来酰亚胺的[3+2]环加成反应

本文报道了在可见光照射下,以10-甲基-9-均三甲苯基吖啶高氯酸盐为光催化剂,室温条件下实现了氮杂环丙烯与马来酰亚胺[3+2]环加成反应,以55-99%的产率合成了二氢吡咯[3,4-c]吡咯-1,3(2H,3aH)二酮类化合物。此外,向反应体系中加入DDQ,可一锅法得到芳构化的吡咯[3,4-c]吡咯-1,3(2H,5H)二酮。该方法具有操作简单、反应条件温、官能团耐受性好等特点。     

Chiral Tertiary Amine Catalyzed Asymmetric [4 + 2] Cyclization of 3-Aroylcoumarines with 2,3-Butadienoate

Coumarins and 2H-pyran derivatives are among the most commonly found structural units in natural products. Therefore, the introduction of 2H-pyran moiety into the coumarin structural unit, i.e., dihydrocoumarin-fused dihydropyranones, is a potentially successful route for the identification of novel bioactive structures, and the synthesis of these structures has attracted continuing research interest. Herein, a chiral tertiary amine catalyzed [4 + 2] cyclization of 3-aroylcoumarines with benzyl 2,3-butadienoate was reported. In the presence of Kumar’s 6’-(4-biphenyl)-β-iso-cinchonine, the desired dihydrocoumarin-fused dihydropyranone products could be obtained in up to 97% yield and 90% ee values.     

9-Hydroxy [7]metacyclophane

A new pyrolytic access to a metacyclophane has been found by the flash vacuum thermolysis of spiro[5,7]trideca-l,4-dien-3-one ($\text{4}$) which gave 9-hydroxy[7]metacyclophane (7) , and 4-(6-heptenyl)phenol (8) . The mechanism of formation of 7 and 8 from the intermediate diradical ($\text{6}$) is discussed.     

Phosphole-Fused Dehydropurpurins via Titanium-Mediated [2+2+1] Cyclization Strategy

A [2+2+1] cyclization strategy of bis(alkynyl)porphyrin using low-valent titanium species, generated in situ, afforded phosphole-fused dehydropurpurins for the first time. The systematic investigations on the electronic properties of the dehydropurpurins revealed their unique features owing to the oxidation states of the phosphorus atom on the fused phosphole ring. The phosphole P=O and P=S derivatives were found to possess high electron-accepting character derived from phosphorus(V) centers without the contribution of 24π antiaromatic character, suggesting their potential utility as electron-accepting materials. In contrast, the phosphorus(III) derivatives revealed different optical and electrochemical properties arising from both 18π aromatic and 24π antiaromatic networks including the lone pair of the phosphorus(III) atom. Overall, the oxidation state of the phosphorus atom has a clear impact on the whole electronic properties, demonstrating the advantages of chemical modifications of the phosphorus center for creating an exotic π-system. The application of titanium-mediated [2+2+1] cyclization to porphyrins is highly promising for expanding a world of heterole-fused porphyrinoids.     

Palladium-promoted Cyclization of Tetra-alkylated 1-Arylazonaphthalenes to 2-Aryl-benzo[g]indazoles

1-Arylazonaphthalenes with all the potential cyclopalladation sites (one peri- and three ortho-positions) substituted by methyl or ethyl groups react with stoicheiometric or catalytic amounts of sodium tetrachloropalladate(II) to the corresponding 2-arylbenzo[g]indazoles. Possible mechanisms for the catalytic cyclization reaction are proposed.     

Die Kristallstrukturen von [Et3PNAsPh3]2[Ag2Br4] und [Et3PNAsPh3]2[Pd2Br6]

Crystal Structures of [Et₃PNAsPh₃]₂[Ag₂Br₄] and [Et₃PNAsPh₃]₂[Pd₂Br₆] Colourless single crystals of [Et₃PNAsPh₃]₂[Ag₂Br₄]( 1 ) and red single crystals of [Et₃PNAsPh₃]₂[Pd₂Br₆]( 2 ) have been isolated from saturated solutions in acetonitrile of equivalent mixtures of [Et₃PNAsPh₃]Br with AgBr and PdBr₂, respectively. Both complexes were characterized by IR spectroscopy and by crystal structure determinations. 1 : Space group P1¯, Z = 1, lattice dimensions at ‐70°C: a = 985.0(2), b = 1042.2(5), c = 1345.8(5) pm, α = 102.88(2)°, β = 105.73(2)°, γ = 94.94(2)°, R₁ = 0.0577. 2 : Space group P2₁/c, Z = 2, lattice dimension at ‐70°C: a = 1003.0(1), b = 1371.8(2), c = 1974.0(1) pm, β = 93.30(1)°, R₁ = 0.0458. The dimeric anions of 1 and 2 form planar, centrosymmetric complex units.