The mechanism of base-promoted HF elimination from 4-fluoro-4-(4'-nitrophenyl)butan-2-one: a multiple isotope effect study including the leaving group (18)F/(19)F KIE.

Leaving-group fluorine as well as the primary and secondary deuterium kinetic isotope effects (KIEs) have been determined for the base-promoted elimination of hydrogen fluoride from 4-fluoro-4-(4'-nitrophenyl)butan-2-one in aqueous solution. The elimination was studied for formate, acetate, and imidazole as the catalyzing base. The fluorine KIEs were determined using the accelerator-produced short-lived radionuclide (18)F in combination with natural (19)F. The (19)F substrate was labeled with (14)C in a remote position to enable radioactivity measurement of both isotopic substrates. The elimination reaction exhibits large primary deuterium KIEs: 3.2, 3.7, and 7.5 for formate, acetate, and imidazole, respectively, thus excluding the E1 mechanism. The corresponding C(4)-secondary deuterium KIEs are 1.038, 1.050 and 1.014 and the leaving group fluorine KIEs are 1.0037, 1.0047 and 1.0013, respectively. The size of the fluorine KIEs corresponds to 5-15% of the estimated maximum of 1.03 for complete C-F bond breakage. No H/D exchange is observed during the reaction. The size and trends of the KIEs for the different bases are consistent with an E1cB-like E2 or an E1cB(ip) mechanism.     

Borderline between E1cB and E2 mechanisms. Chlorine isotope effects in base-promoted elimination Reactions.

The chlorine leaving group isotope effect has been measured for the base-promoted elimination reaction of 1-(2-chloro-2-propyl)indene (1-Cl) in methanol at 30 degrees C: k(35)/k(37) = 1.0086 +/- 0.0007 with methoxide as the base and k(35)/k(37) = 1.0101 +/- 0.0001 with triethylamine (TEA) as the base. These very large chlorine isotope effects combined with large kinetic deuterium isotope effects of 7.1 and 8.4, respectively, are consistent not with the irreversible E1cB mechanism proposed previously (J. Am. Chem. Soc. 1977, 99, 7926) but with the E2 mechanism with transition states having large amounts of hydron transfer and very extensive cleavage of the bond to chlorine.     

Condensation reactions at the methylene group of 1-(4-nitrophenyl)-pyrrolin-2-one and 1-(4-nitrophenyl)-pyrrolin-2-onium perchlorate

The interaction has been investigated of 1-(4-nitrophenyl)pyrrolin-2-one with aromatic aldehydes in acetic anhydride in the presence of catalytic amounts of pyridine. 1-(4-Nitrophenyl)pyrrolinium perchlorate has been synthesized and was put into a condensation reaction with aromatic aldehydes. As a result 5-arylidene-1-(4-nitrophenyl)pyrrolin-2-onium perchlorates were obtained. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1015–1021, July, 2006.     

用Heck反应合成1-羟基-4-(3-吡啶基)丁-2-酮

在Heck反应条件下,以Ph3P为催化剂配体,由3-卤代吡啶和3-丁烯-1,2-二醇进行偶合可以得到1-羟基-4-(3-吡啶基)丁-2-酮,具有原料易得、合成方法简单的优点.     

Unprecedented syntheses of 1,5-difluoropentan-3-amine and 4-fluoro-2-(2-fluoroethyl)butan-1-amine

Herein, we report two synthetically useful and high yielding routes to so far unknown branched γ,γ′- and δ,δ′-difluoroalkylamines that can be of interest as building-blocks for medicinal chemistry programs.     

Syntheses Based on 4-(2-Hydroxy-4-methylquinolin-3-yl)butan-2-one Thiosemicarbazones

Russian Journal of Organic Chemistry - Thiazolidine and thiazolidinone derivatives containing a quinoline fragment have been synthesized by heterocyclizations of...     

1,3-Dipolar cycloaddition of diarylnitrones to 1-(4-nitrophenyl)-5H-pyrrolin-2-one

The reaction of diarylnitrones with 1-(4-nitrophenyl)-5H-pyrrolin-2-one to give 2-oxa-6-oxo-3-phenyl-4-(R-phenyl)-7-(4-nitrophenyl)-3,7-diazabicyclo(3,3,0)octanes has been examined. The structures of the products were established by NMR and IR spectroscopy, and x-ray diffraction studies. The stereoselectivity of the reaction is due to exo-approach of the reactants with cis-stereospecific addition of the trans-forms of the C,N-diarylnitrones to the pyrrolinone double bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1675–1678, December, 1990.     

Radical addition reaction of alcohols to 1-(4-nitrophenyl)-5H-pyrrolin-2-one

Quantum chemical calculations of the parameters of the 1-(4-nitrophenyl)-5H-pyrrolin-2-one molecule have been carried out by the MNDO method. The radical addition reaction of aliphatic, alicyclic, and aromatic alcohols to 1-(4-nitrophenyl)-5H-pyrrolin-2-one with the formation of 3- and 4-substituted pyrrolidones has been investigated.Kuban State Technological University, Krasnodar 350072, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 934–938, July, 1998.     

Preparation of 1-(4-nitrophenyl)-2-formylpyrrole from furfural

The products of the condensation of furfural with p-nitroaniline in an acidic medium in various solvents were investigated. It was established that the well-known method gives 1-(4-nitrophenyl)-2-formylpyrrole in no higher than 55% yield and 2,3-bis(4-nitrophenylamino)-2-formylpyrrole in 27% yield. A method based on a previously described method is recommended (the products are obtained in up to 72% yields).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1062–1066, August, 1981.     

Bromination of 1-(4-nitrophenyl)-2-formylpyrrole

Depending on the amount of bromine, the bromination of 1-(4-nitrophenyl)-2-formylpyrrole with bromine in chloroform without a catalyst gives 5-bromo and 4,5-dibromo derivatives. 4-Bromo-1-(4-nitrophenyl)-2-formylpyrrole is formed in the presence of excess AlC1₃, while a mixture of 3,4- and 4,5-dibromo derivatives with preponderance of the latter is formed with excess bromine. The results are compared with the literature data on the bromination of 2-formylpyrrole, 2-formylfuran, and 2-formylthiophene and are interpreted with allowance for the electronacceptor effect of the p-nitrophenyl substituent attached to the nitrogen atom of the pyrrole ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 662–665, May, 1982.     

Oxidation of 1-(4-nitrophenyl)-2-formylpyrrole

Pyrrole aldehydes interact with oxidizing agents to yield products which are oxidized to different degrees. Pyrrolecarboxylic acids are formed under the influence of silver oxides, an alkaline solution of permanganate, and 2–10% sulfuric acid [1–3]. With peroxidation of hydrogen, 5-unsubstituted pyrrole aldehydes convert to pyrrolone [4], and pyrrol-2-aldehyde converts to succinimide [5]. Chromacetate and chromium sulfuric acids oxidize pyrrole aldehydes to maleinimides [3].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 495–499, April, 1982.     

The base-promoted dehydration of rac.-trans-tetrahydro-6-hydroxy-4-[(2-(dimethylamino)ethyl]-7-(4-methoxyphenyl)-1,4-thiazepin-5(2H)-one

The base-catalyzed alkylation of rac.-trans-tetrahydro-6-hydroxy-7-(4-methoxyphenyl)-1,4-thiazepin-5(2H)-one ( 1 ) with dimethylaminoethyl chloride in dimethyl sulfoxide provided predominantly rac.-trans-tetrahydro-6-hydroxy-4-[(2-dimethylamino)ethyl]-7-(4-methoxyphenyl)-1,4-thiazepin-5(2H)-one ( 2 ) and in addition, 2,3-dihydro-4-[2-(dimethylamino)-ethyl]-7-(4-methoxyphenyl)-1,4-thiazepin-5(4H)-one ( 3 ). A plausible mechanism is postulated for the dehydration of the rac.-trans-amide 2 .