Microwave-assisted cross-coupling of 3-chloro-2-pyrazolines and 3-chloro-1-phenyl-1,4,5,6-tetrahydropyridazine with aryl boronic acids

3-Chloro-1-phenyl-2-pyrazoline and 3-chloro-1-phenyl-1,4,5,6-tetrahydropyridazine were coupled with aryl boronic acids in good yields under microwave heating conditions (140 °C, 5 min).     

4,4-Dialkyl-substituted N-Methylmorpholinium 3,5-Dicyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates and Some of Their Properties

4,4-Dialkyl-substituted N-methylmorpholinium 3,5-dicyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates were synthesized by the condensation of 2-alkyl-2-cyanoethyl crotonates with cyanothioacetamide and N-methylmorpholine. They were used for the production of substituted 2-alkylthio-1,4,5,6-tetrahydropyridines, 2-acetylthio-1,4,5,6,-tetrahydropyridine, 6-hydrazino-1,4,5,6-tetrahydropyridine, and 2,3,4,5,6,7-hexahydrothiazolo[3,2-a]pyridine. The structure of 6-bromo-3-bromomethyl-6,8-dicyano-7,7-dimethyl-2,3,4,5,6,7-hexahydrothiazolo[3,2-a]pyridine was proved by X-ray crystallographic analysis.     

Synthesis of 1,3,4‐Oxadiazoles and 1,3‐Thiazolidinones Containing 1,4,5,6‐Tetrahydro‐6‐pyridazinone

The reaction of 1,4,5,6‐tetrahydro‐6‐pyridazinone‐3‐carboxylic acid hydrazides ( 1 ) with aromatic aldehydes afforded 1,4,5,6‐tetrahydro‐6‐pyridazinone‐3‐carbonyl aromatic aldehyde hydrazones ( 2a‐2g ). Heterocyclic derivatives linked 1,3,4‐oxadiazole obtained by cyclocondensation of 2a‐2g with acetic anhydride in absolute ethanol, and 2a‐2g cyclized with mercaptoacetic acid in DMF in the presence of anhydrous ZnCl₂ afforded the 1,3‐thiazolidinone derivatives. The structures of the new compounds were established by elemental analyses, IR, ¹H NMR and MS spectral data.     

1,4,5,6-Tetrahydro-1,2,4-triazin-6-ones and 3-amino-1-imidazolin-4-ones from 2-aminoacylhydrazines

The 2-aminoacylhydrazines form 1,4,5,6-tetrahydro-1,2,4-triazin-6-ones with orthoesters and iminoesters. Benzylidene and isopropylidene derivatives of the 2-aminoacylhydrazines give the corresponding derivatives of 3-amino-1-imidazolin-4-ones with the same reagents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1388–1391, October, 1991.     

(4+2)-Cycloadditionen von intermediärem 1-Phenyl-1-phenylazo-äthylen (α-Phenylazo-styrol)

1-Phenyl-1-phenylazoethylene (α-phenylazostyrene,2) cannot be isolated, as, functioning both as a heterodiene and a dienophile, it reacts to its (4+2)-cyclodimer, 1,3,6-triphenyl-6-phenylazo-1,4,5,6-tetrahydropyridazine (3). In the presence of the competing dienophile 3-buten-2-one (4) the intermediate2 is partially trapped to 6-acetyl-1,3-diphenyl-1,4,5,6-tetrahydropyridazine (5).     

Synthesis of tailor-made 1-aryl-2-arylamino-4-imino-1,4,5,6-tetrahydro-1,3,5-triazine-6-thiones

Reaction of 1-amidino-3-arylthioureas (1) with aryl isothiocyanates yielded 1-aryl-2-arylamino-4-imino-1,4,5,6-tetrahydro-1,3,5-triazine-6-thiones (3) which contained the more electron releasing aryl substituent at the ring nitrogen. The reaction of the S-benzyl derivatives of (1) with aryl isothiocyanates could be directed to give the same type of triazinethione derivatives but with the desired aryl substituent at the ring nitrogen.     

1,3,6-Triphenyl-6-phenylazo-1,4,5,6-tetrahydropyridazin

Base induced 1.4-elimination of pyridine·HI from 1-(2-phenyl-2-phenylhydrazono-ethyl)-pyridinium iodide (6) yields 1.3.6-triphenyl-6-phenylazo-1.4.5.6-tetrahydropyridazine (8) the (4+2)-cyclodimer of the intermediate 1-phenyl-1-phenylazoethylene (7).8 can also be obtained by intramolecular oxidative cyclisation (with KMnO₄) of 1.4-diphenylbutane-1.4-dione bisphenylhydrazone (12). Spectroscopic data (ms,¹H-nmr, uv and ir/Raman) confirm the structure of8.     

A novel approach to the pyrido[4,3-c]pyridazine ring. Synthesis of pyrido[4,3-c]pyridazin-5(6H)-one from 3,4-disubstituted pyridazines

The synthesis of new pyrido[4,3-c]pyridazin-5(6H)-one from ethyl 3-methyl-4-pyridazinecarboxylate using an enamination/ring closure sequence is described. The starting material is easily available from a hetero Diels-Alder reaction between a 1,2-diaza-1,3-diene and ethyl vinyl ether and oxidation of the resulting 1,4,5,6-tetrahydropyridazine.     

Synthesis and Alkylation of N-Methylmorpholinium 4-Aryl-3,5-dicyano-6-oxo-1,4,5,6-tetrahydro-2-pyridinethiolates. Molecular and Crystal Structure of 4,5-trans-3,5-Dicyano-4-(2-methoxyphenyl)-2-methylthio-6-oxo-1,4,5,6-tetrahydropyridine

The reaction of aromatic aldehydes with cyanothioacetamide and ethyl cyanoacetate in the presence of N-methylmorpholine gives N-methylmorpholinium 4-aryl-3,5-dicyano-6-oxo-1,4,5,6-tetrahydro-2-pyridinethiolates, which are used in the synthesis of substituted 2-alkylthiotetrahydropyridines. X-ray diffraction analysis was used to study the structure of 4,5-trans-3,5-dicyano-4-(2-methoxyphenyl)-2-methylthio-6-oxo-1,4,5,6-tetrahydropyridine.     

Tricomponent domino synthesis of 6-hydroxy-2-chloro-1,4,5,6-tetrahydropyridine-3,4,4-tricarbonitriles

In reaction of tetracyanoethylene with ketones and HCl in 1,4-dioxane at 30–40°? 6-hydroxy-2-chloro-1,4,5,6-tetrahydropyridine-3,4,4-tricarbonitriles are formed.     

Some reactions of 2-methyl-3-ethoxycarbonyl-1,4,5,6-tetrahydropyridine-6-thione

2-Methyl-3-ethoxycarbonyl-1,4,5,6-tetrahydropyridine-6-thione was synthesized, and its reactions at the methylene and thioketo groups were investigated. The absorption spectra in the visible region were obtained for the dyes thus synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 225–227, February, 1971.     

Synthesis and characterization of N-substituted 1,4,5,6-tetrahydropyrimidine containing functional polymers as SO2 and CO2 sorbents

Novel vinyl monomers containing 1,4,5,6-tetrahydropyrimidine were prepared by the reaction of N-substituted-1,3-diaminopropane with N,N-dimethyl-formamide dimethylacetal, which gave 1-alkyl or aryl substituted 1,4,5,6-tetrahydropyrimidines, Alkylation of the tetrahydropyrimidine derivatives by chloromethylstyrene produces the N-methyl-N′-vinyl benzyl-1,4,5,6-tetrahydropyrimidinium chloride in high yields. These monomers were readily polymerized in dimethylformamide by AIBN at 80°C. Homopolymers and soluble linear copolymers were prepared and copolymerization parameters were rationalized. Further, insoluble terpolymers prepared from these monomers, styrene and divinylbenzene were tested for the sorption of the weakly acidic gases gave excellent results. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2411–2420, 1997     

A convenient synthesis of pyridazine-3,4-dicarboxylic acid by a hetero diels-alder reaction

A convenient route to prepare unsubstituted pyridazine-3,4-dicarboxylic acid on a preparative scale is described. The synthesis involves a hetero Diels-Alder reaction between a new 1,2-diaza-1,3-diene and ethyl vinyl ether and oxidation of the intermediate 1,4,5,6-tetrahydropyridazine as the key step.     

Studies on the Fischer indole synthesis: Behaviour of cyclic hydrazones of tetrahydropyridazine and pyrazoline series in polyphosphoric acid.

Heating 1,3-diphenyl-1,4,5,6-tetrahydropyridazine in PPA affords mainly 4-benzoyl-1,2,3,4-tetrahydroquinoline and 2-anilinopropiophenone. In analogous conditions 1,5-diphenyl-3-methyl-2-pyrazoline gives 2-styrylindole, benzidine and benzylideneacetone.     

The Mannich reaction in the synthesis of N,S-containing heterocycles 8. Aminomethylation of 3,5-dicyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates as a method for the synthesis of new functionally substituted 3,7-diazabicyclo[3.3.1]nonane derivatives

Aminomethylation of 3,5-dicyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates upon treatment with primary amines and excess formaldehyde leads to 3,7-diazabicyclo[3.3.1]nonane derivatives. N-Methylmorpholinium 4-(2-chlorophenyl)-3,5-dicyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolate was obtained by the reaction of (E)-3-(2-chlorophenyl)-2-cyanoprop-2-enethioamide with 1-cyanoacetyl-3,5-dimethylpyrazole and N-methylmorpholine in acetone in quantitative yield. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2397–2400, December, 2007.     

Synthesis of optically active 1,2,3-substituted-1,4,5,6-tetrahydro-7H-indolones

Trisubstituted 1,4,5,6,-tetrahydro-7H-indolones are obtained in a one-pot synthesis from conjugated nitroolefins and α-ketoenamines derived from α-amino esters and cyclohexane-1,2-dione. In some cases bicyclo[3.2.1]octan-8-one and 1,2-oxazine N-oxide derivatives are isolated.     

Stereoselective Synthesis and Alkylation of N-Methylmorpholinium 4,5-trans-4-(2-chlorophenyl)-3-cyano-6-hydroxy-5-(2-thenoyl)-6-trifluoromethyl-1,4,5,6-tetrahydropyridine-2-thiolate. Molecular and Crystal Structure of 4,5-trans-4-(2-chlorophenyl)-3-cyano-6-hydroxy-2-methallylthio-5-(2-thenoyl)-6-trifluoromethyl-1,4,5,6-tetrahydropyridine

The condensation of 2-chlorobenzaldehyde with cyanothioacetamide and 2-thenoyltrifluoroacetone in the presence of N-methylmorpholine takes place stereoselectively and leads to the formation of N-methylmorpholinium 4,5-trans-4-(2-chlorophenyl)-3-cyano-6-hydroxy-5-(2-thenoyl)-6-trifluoromethyl-1,4,5,6-tetrahydropyridine-2-thiolate. The latter was used to synthesize the corresponding 2-alkylthiotetrahydropyridines. The structure of 4,5-trans-4-(2-chlorophenyl)-3-cyano-6-hydroxy-2-methallylthio-5-(2-thenoyl)-6-trifluoromethyl-1,4,5,6-tetrahydropyridine was determined by X-ray crystallographic analysis.     

Regioselective synthesis of 6-trifluoromethyl-1,4,5,6-tetrahydropyrazolo[3,4-b]pyran derivatives

A facile two-step procedure for the synthesis of 6-(trifluoromethyl)-1,4,5,6-tetrahydropyrazolo[3,4-b]pyran derivatives (4) from the reaction of 4-arylidene-3-methyl-1-phenyl-5-pyrazolones (1) with ethyl trifluoroacetoacetate (2), a versatile fluorinated building-block, was presented. Furthermore, to increase the efficiency of this reaction, the more convenient one-pot three-component process was also developed with a slightly lower yield. Treatment of 4 with P₂O₅, conc. H₂SO₄, POCl₃/Py or p-TsOH under the drastic conditions did not afford the corresponding dehydrated products.     

Synthesis of 1,4,5,6-tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-5-enylmethyl haloacetates

The possibility of preparing 1,4,5,6-tetrachloro-7,7-dimethoxybicyclo[2.2.1]hept-5-enylmethyl haloacetates by the reaction of tetrachlorodimethoxycyclopentadiene with allyl haloacetates was examined. The effect of various factors on the product yield was studied, and the optimal synthesis conditions were found.     

Synthesis and Properties of Ammonium 5-Benzoyl-4-(2-chlorophenyl)-3-cyano-6-hydroxy-6-phenyl-1,4,5,6-tetrahydropyridine-2-thiolates

The reaction of 2-chlorobenzaldehyde with cyanothioacetamide and dibenzoylmethane in the presence of piperidine or N-methylmorpholine gave the corresponding 5-benzoyl-4-(2-chlorophenyl)-3-cyano-6-hydroxy-6-phenyl-1,4,5,6-tetrahydropyridine-2-thiolates, used in the synthesis of 1-alkylthio-4-benzoyl-1-benzoylamino-3-(2-chlorophenyl)-2-cyanobut-1-enes.