Photo valence isomerization of sterically strained aromatic hydrocarbons: 8,9-dicarbethoxy[6]paracyclophane

Irradiation of 8,9-dicarbethoxy[6]paracyclophane (1) in the long-wavelength band with λ ≈ 310 nm in dilute fluid solutions gives the 1,4-Dewar isomer (2) with 2.4% quantum yield. The thermal back reaction 2 → 1 follows an Arrhenius law (E_a = 88.3 ± 3.6 kJmol^-1, logA = 9.3 ± 0.6). By calorimetry an enthalpy of this reaction was determined as δH = -19.8 ± 3.8 kJmol^-1. This is significantly smaller than in unstrained systems with a planar aromatic ground state. No other products were detected in this thermoreversible photoreaction. The photochemical rearomatization 2 → 1 occurs with a quantum yield of 0.12 ± 0.02 with light of λ ≈ 288 nm. Only by irradiation of 2 with λ < 270 nm the prismane isomer (3) is formed.     

A new synthesis of 2,3-dihydrofuro[2,3-b], [2,3-c] and [3,2-c]quinolines

A new synthesis of three isomeric dihydrofuroquinolines is described. This route via ortholithiation of O-quinolyl carbamates is considerably more effective than that which proceeds via lithiation of alkoxyquinolines.     

A new simple approach to the [6] (2,5)pyridinophane ring system

Upon treatment with [Mo(CO)₆], 3-phenyl-4,5-hexamethyleneisoxazole undergoes an inclusion of acetylenic ester across the C₄-C₅ bond and elimination of an oxygen atom leading to [6](2,5)pyridinophane derivative.     

A new one-step synthesis of 2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one and 3,4-dihydro-2h,6h[1,3]thiazino[2,3-b] quinazolin-6-one

2,3-Dihydro-5H-thiazolo[2,3-b]quinazolin-5-one and 3,4-dihydro-2H,6H[1,3] thiazino[2,3-b]-quinazolin-6-one have been synthesized in one step by the reaction of methyl anthranilate with ehloroalkyl isothiocyanates.     

A new approach to the synthesis of pyridazino[4,5-c]pyridazinones

The reaction of 5-hydrazinopyridazin-3(2H)-ones 1 with α-keto diester 2 in acetic acid afforded the corresponding 4,6-dihydropyridazino[4,5-c]pyridazin-5(1H)-ones 3 and pyrrolo[2,3-d)pyridazin-4(5H)-ones 4 . Compounds 3 were also obtained from 4-bromo-5-hydrazinopyridazin-3(2H)-ones 8 and 2 under milder conditions. 5-Bromo-4-hydrazinopyridazin-3(2H)-one 9 , the regioisomer of 8b , also reacted readily with 2a to give 4,7-dihydropyridazino[4,5-c]pyridazin-8(1H)-one 10b , the regioisomer of 3b .     

A new synthesis of p-nitrocalix[6]arene

p-Nitrocalix[6]arene which possibly serves as a potential intermediate to derive functionalized calixarenes was synthesized for the first time.     

A new synthesis of naphtho[2,3-C]pyrroles. Conversion of naphtho[2,3-C]thiophene-4,9-diones to naphtho[2,3-C]pyrrole-4,9-diones

A series of 2-substituted-4,9-dihydronaphtho[2,3-c]pyrrole-4,9-diones was prepared by the reaction of 4,9-dihydronaphtho[2,3-c]thiophene-4,9-diones with primary amines under mild conditions. The presence of halogen in the naphtho[2,3-c]thiophene-4,9-dione and the presence of hydroxyl, ether, or tertiary amine functions in the amine reagent do not interfere with the course of the reaction.     

Reactions of anthranilamide with isocyanates: A new facile synthesis of 2,3-dihydro-5H-oxazolo[2,3-b]quinazolin-5-one and 3,4-dihydro-2H,6H-[1,3]oxazino[2,3-b]quinazolin-6-one [1]

2,3-Dihydro-5H-oxazolo[2,3-b]quinazolin-5-one 5a was synthesized from anthranilamide 1 and 2-chloro-ethyl isocyanate either by a direct reflux in methanol, or by stirring at room temperature in acetonitrile leading to the intermediate, 2-(2-chloroethyl ureido)benzamide 6a which was subsequently cyclized on heating with an organic base. However, when compound 6a was refluxed with concentrated hydrochloric acid, it furnished 3-(2-chloroethyl)-2,4-dioxo-1H,3H-quinazoline 2a in good yields. 3,4-Dihydro-2H,6.H-[1,3]-oxazino[2,3-b]quinazolin-6-one 5b , 3-(3-chloropropyl)-2,4-dioxo-1H,3.H-quinazoline 2b and 2-(3-chloropropyl ureido)benzamide 6b were obtained similarly from 1 and 3-chloropropyl isocyanate.     

Porphyrin system containing [2.2]paracyclophane units

Meso-tetrakis([2.2]paracyclophanyl)porphyrin was obtained from [2.2]paracyclophanecarbaldehyde and pyrrole. Replacement of phenyl groups in meso-tetraphenylporphyrin by paracyclophanyl substituents remarkably influences the electronic structure of the molecule, causing bathochromic shifts of all uv-vis absorption bands, and changing the ring current of the porphyrin core. The shifts in the electron spectrum are substantially greater than those observed for other porphyrin derivatives characterized by their extended π-electron systems, such as meso-tetrakis(2-phenylethenyl)porphyrin and meso-tetrakisbiphenylporphyrin.     

A new approach to the synthesis of pyrrolo[1,2-a]indole derivatives

Reactions of 2-(3,3-diamino-2-cyanoprop-2-enylidene)indolin-3-ones with amide acetals afforded derivatives of 3-aminomethyleneamino-2-cyano-9-oxo-9H-pyrrolo[1,2-a]indole and 3-amino-2-cyano-9-oxo-9H-pyrrolo[1,2-a]indole. The rate and pathway of the reaction depend on the reagents and solvents. The formation schemes for the compounds obtained were proposed. Their structures were proven by IR and ¹H NMR spectroscopy and mass spectrometry and confirmed by independent syntheses. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2186–2192, December, 2006.     

Synthesis of new 6-Aroylpyrido[2,3-d]pyrimidines

The synthesis of 6-dimethylaminomethylenaminopyrimidin-4(3H)-ones 2 and its reaction with β-dimethyl-aminopropiophenone hydrochloride 3 is discussed in this work. The reaction of 6-aminopyrimidin-4(3H)-ones 1 with an excess of dimethylformamide dimethyl acetal gives rise to the formation of 6-dimethylaminomethyleneaminopyrimidines 2. The heating of equimolecular quantities of 2 and 3 in dimethylformamide leads to the 6-aroylpyrido[2,3-d]pyrimidines derivatives 4. The structures of compounds 2 and 4 were determined on the basis of nmr measurements.     

Condensed pyridine bases. A new approach to the synthesis of 3-phenacylbenzo[b]thiophenes and 3-phenacyl-5-ethylthieno[2,3-b]thiophene. Synthesis of new derivatives of benzothieno[2,3-c]pyrylium and thieno[2′,3′:5,4]thieno-[2,3-c]pyrylium and pyridine bases

A new method is proposed for the production of substituted 3-phenacylbenzo[b]thiophenes by the intramolecular cyclization of 1-phenyl-4-phenylthio-1,3-butanediones in polyphosphoric acid. The analogous cyclization of 1-phenyl-4-(5-ethyl-2-thienylthio)-1,3-butanedione leads to 3-phenacyl-5-ethylthieno[2,3-b]thiophene. The acylation of substituted 3-phenacylbenzo[b]thiophenes and 3-phenacyl-5-ethylthieno[2,3-b]thiophene by the anhydrides of aliphatic acids in the presence of perchloric acid leads to 1-alkyl-3-phenylbenzothieno[2,3-c]pyrylium perchlorates and 2-ethyl-5-phenyl-7-methylthieno[2′,3′:5,4]thieno[2,3-c]pyrylium perchlorate. The action of ammonium acetate on the obtained salts gives the corresponding pyridine bases. L. M. Litvinenko Institute of Physical Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine, Donetsk 340114. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1335–1339, October, 1998.     

The synthesis of a pyrido[2,3-c]pyridazine: A cinnoline related to 6-fluoronalidixic acid

An analog of the pyrido[2,3-c]pyridazine ring system, 1-ethyl-6-fluoro-1,4-dihydro-7-methyl-4-oxopyrido-[2,3-c]pyridazine-3-carboxylic acid ( 13 ), related to both Cinoxacin ( 1 ) and nalidixic acid ( 2 ), has been synthesized. The reductive ring closure of 2-chloro-α-diazo-6-methyl-5-nitro-β-oxo-3-pyridinepropanoic acid, ethyl ester ( 7 ), proved to be the key reaction providing entry into the ring system.     

The synthesis of enantiomerically pure [2.2]paracyclophane derivatives

[2.2]Paracyclophane is a fascinating molecule that offers great potential in a wide range of chemical disciplines. Currently, the synthesis of the majority of enantiomerically pure [2.2]paracyclophane derivatives is based on the resolution of a small number of starting materials or individual resolution procedures are developed for each new compound. The development of more general routes to these valuable compounds via the resolution of a common intermediate is discussed. Ultimately, it would be preferable to synthesise these valuable compounds without recourse to resolution and ideas for this rewarding goal are postulated.     

Attempts at new synthesis of 5,11 -Dihydro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one

Attempting some new approaches to 5,11-dihyro-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one ( 6 ), compounds 8, 10 and 11 were prepared. Ring enlargement of 4 into 6 failed, as well as condensation of 10 and 11 into ID, which is the potential precursor of pirenzepin (11-[2′-(4″-methylpiperazin-1″-yl)]acetyl derivative of 6 ) via an envisaged intramolecular Diels-Alder reaction. Model compounds 5 and 13 were prepared and their behaviour in analogous reactions explained the failures of the intended transformations of 4 , as well as of condensation of 10 and 11 .     

Electroorganic synthesis of new benzofuro[2,3-d]pyrimidine derivatives

Electrochemical oxidation of 3,4-dihydroxybenzoic acid (1) in the presence of 1,3-dimethylbarbituric acid (2) and 1,3-diethyl-2-thiobarbituric acid (3) as nucleophiles in aqueous solution has been studied using cyclic voltammetry and controlled-potential coulometry. The results indicate that 1 via Michael reaction under electro-decarboxylation reaction converts to benzofuro[2,3-d]pyrimidine derivatives (6a, 6b). The electrochemical synthesis of 6a, 6b has been successfully performed in an undivided cell in good yields and purity.     

A new approach to the synthesis of trifluoromethylated products of the [3,3]-sigmatropic rearrangement

CH-acids of general formula CF₃CH(X)CF₃ (X = CF₃, CO₂R) react with 2,3-unsaturated alcohols in the presence of bases to give trifluoromethylated products of the [3,3]-sigmatropic rearrangement. These reactions provide a convenient method for the synthesis of 2-alkenyl-2-trifluoromethylmalonates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1273–1277, July, 1994.