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Curt Wentrup - One of the best experts on this subject based on the ideXlab platform.
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Printed in Great Britain. (B 1997 IUPAC Photochemistry of pyridyl azides and diazo ketones in matrix and in solution
2015Co-Authors: Curt Wentrup, Peter VissepAbstract:Abstract: This paper describes recent advances in the photochemistry of 2-pyridyl azides/tetrazolo[l,5a]pyridines, which is a viable synthetic source of novel 13-Diazepines via ring expansion of the 2-pyndylnitrenes to 1,3-diazacycloheptatetraenes. The nitrenes have been observed by Ar matrix ESR spectroscopy, and the diazacycloheptatetraenes by Ar matrix IR spectroscopy. Trapping with nucleophiles in solution at room temperature leads to lHi-1,3-Diazepines, some of which are stable, distillable compounds, whereas others isomerize to stable 5H-13-Diazepines. New chemistry in the field of Wolff rearrangement of pyridine-based dimketones leads to 2- and 3-azafulvenones, which dimerize or tetramerize at extremely low temperatures (40- 70 K). These facile reactions are thought to involve ketene-nucleophile ylide (zwitterion) intermediates. It was found that ketenes react with pyridine to form related ylides at temperatures as low as 15- 40 K. INTRODUCI'ION The rearrangements and interconversions of arylcarbenes and arylnitrenes have been the subject of several reviews ( l) , and the energy surface connecting the phenylcarbene isomers (1- 3 and others) has recentl
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4-Pyridylnitrene and 2-pyrazinylcarbene
2013Co-Authors: Ales Reisinger, Curt Wentrup, David Kvaskoff, Beilstein Org J. ChemAbstract:carbene–nitrene interconversion; Diazepines; flash vacuum thermolysis; matrix photochemistry; nitrile ylides; reactive intermediate
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1H-1,3-Diazepines, 5H-1,3-Diazepines, 1,3-diazepinones, and 2,4-diazabicyclo[3.2.0]heptenes.
Organic & biomolecular chemistry, 2004Co-Authors: Ales Reisinger, Paul V. Bernhardt, Rainer Koch, Curt WentrupAbstract:Tetrazolo[1,5-a]pyridines/2-azidopyridines 1 undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes 3, which react with alcohols to afford 2-alkoxy-1H-1,3-Diazepines 4 (5), with secondary amines to 2-dialkylamino-5H-1,3-Diazepines 16, sometimes via isolable 2-dialkylamino-1H-1,3-Diazepines 15, and with water to 1,3-diazepin-2-ones 19. The latter are also obtained by elimination of isobutene or propene from 2-tert-butoxy- or 2-isopropoxy-1H-1,3-Diazepines 4 or 5. 1,3-Diazepin-2-one 22B and 1,3-diazepin-4-one 24 were obtained from hydrolysis of the corresponding 4-chloroDiazepines. Diazepinones 19 undergo photochemical ring closure to diazabicycloheptenones 25 in high yields. The 2-alkoxy-1H-1,3-Diazepines 4 and 5 interconvert by rapid proton exchange between positions N1 and N3. The free energies of activation for the proton exchange were measured by the Forsen–Hoffman method as ΔG‡298 = 16.2 ± 0.6 kcal mol−1 as an average for 4a–c in CD2Cl2, acetone-d6, and methanol-d4, and 14.1 ± 0.6 kcal mol−1 for 4c in acetone/D2O. The structures of 2-methoxy-5,6-bis(trifluoromethyl)-1H-1,3-diazepine 4k, 1,2-dihydro-4-diethylamino-5H-1,3-diazepin-2-one 22bB, and diazabicycloheptanone 26 were determined by X-ray crystallography. The former represents the first reported X-ray crystal structure of any monocyclic N-unsubstituted 1H-azepine.
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Synthesis of 1,3-Diazepines and ring contraction to cyanopyrroles.
Organic & biomolecular chemistry, 2003Co-Authors: Ales Reisinger, Paul V. Bernhardt, Curt WentrupAbstract:Several tetrazolo[1,5-a]pyridines/2-azidopyridines undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes (7,10,13,16,19,22) as well as ring cleavage to cyanovinylketenimines (8,17,20b) in low temperature Ar matrices. 6,8-Dichlorotetrazolo[1,5-a]pyridine/2-azido-3,5-dichloropridine 6 undergoes ready exchange of the chlorine in position 8 (3) with ROH/RONa. 8-Chloro-6-trifluoromethyltetrazolo[1,5-a]pyridine 15 undergoes solvolysis of the CF3 group to afford 8-chloro-6-methoxycarbonyltetrazolo[1,5-a]pyridine 18. Several tetrazolopyridines/2-azidopyridines afford 1H- or 5H-1,3-Diazepines in good yields on photolysis in the presence of alcohols or amines (11,14,23,25). 5-Chlorotetrazolo[1,5-a]pyridines/2-azido-6-chloropyridines 21 and 38 undergo a rearrangement to 1H- and 3H-3-cyanopyrroles 27 and 45, respectively. The mechanism of this rearrangement was investigated by 15N-labelling and takes place via transient 1,3-Diazepines. The structures of 6,8-dichloro-tetrazolo[1,5-a]pyridine 6T, 6-chloro-8-ethoxytetrazolo[1,5-a]pyridine 9Tb, dipyrrolylmethane 28, and 2-isopropoxy-4-dimethylamino-5H-1,3-diazepine 25b were determined by X-ray crystallography. In the latter case, this represents the first reported X-ray crystal structure of a 5H-1,3-diazepine.
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SYNTHESIS OF 1H- AND 5H-1,3-Diazepines FROM AZIDO- AND TETRAZOLO-PYRIDINES
Chemical Communications, 1996Co-Authors: A. Reisinger, Curt WentrupAbstract:Stable 1H-1,3-Diazepines 7–9,10,13,14,17 and 19 are obtained, often in high yields, by photolysis of triflouoromethyl-substituted azido- or tetrazolo-pyridines in the presence of alcohols or amines; in some cases 5H-1,3-Diazepines are also formed(11,21 and 23).
Lorenzo Tei - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of 6-Substituted 6-Nitroperhydro-1,4-Diazepines via Novel Tandem Retro-Henry and Mannich/Michael Reactions
2016Co-Authors: Jonathan Martinelli, Giuseppe Gugliotta, Lorenzo TeiAbstract:N,N′-Dibenzyl-6-hydroxymethyl-6-nitroperhydro-1,4-diazepine was converted into a nitronate via retro-Henry reaction, followed by either Michael reaction with several acrylic derivatives or Mannich reaction with different amines, thus leading to 6-substituted 6-nitroperhydro-1,4-Diazepines. The tandem retro-Henry/Mannich reaction was also carried out using benzylamine as base, solvent, and reagent at the same time. Selective hydrogenation of the nitro group and complete hydrogenolysis were also successfully achieved
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synthesis of 6 substituted 6 nitroperhydro 1 4 Diazepines via novel tandem retro henry and mannich michael reactions
Organic Letters, 2012Co-Authors: Jonathan Martinelli, Giuseppe Gugliotta, Lorenzo TeiAbstract:N,N′-Dibenzyl-6-hydroxymethyl-6-nitroperhydro-1,4-diazepine was converted into a nitronate via retro-Henry reaction, followed by either Michael reaction with several acrylic derivatives or Mannich reaction with different amines, thus leading to 6-substituted 6-nitroperhydro-1,4-Diazepines. The tandem retro-Henry/Mannich reaction was also carried out using benzylamine as base, solvent, and reagent at the same time. Selective hydrogenation of the nitro group and complete hydrogenolysis were also successfully achieved.
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A New, Easy Access to the 6-Aminoperhydro-1,4-diazepine Scaffold under Ultrasound and Microwave Irradiation
Synthesis, 2008Co-Authors: Alessandro Barge, Silvia Fuzerova, Dharita J. Upadhyaya, Davide Garella, Silvio Aime, Lorenzo Tei, Giancarlo CravottoAbstract:A novel, efficient, and rapid synthesis of the 6-amino-perhydro-1,4-diazepine scaffold is reported. It was promoted by microwave or sequential ultrasound/microwave irradiation under solvent-free conditions or in solution. Protected ethylenediamine derivatives and N-Boc-serinol dimesylate underwent rapid cyclization to give 6-aminoperhydro-1,4-diazepine derivatives in excellent yields and with high selectivity, whereas the same reaction failed or gave negligible yields under conventional heating. Cesium or potassium ions catalyzed the ring closure by coordinating the sulfon-amide groups. All relevant work reported to date in the literature mostly concern about the syntheses of either 1 H-tetrahydro-1,4-diazepine-2,5-dione or substituted 1,4-benzoDiazepines, while the few published procedures for the preparation of 6-aminoperhydro-1,4-Diazepines involved several steps, required long reaction times and afforded low yields. By the present method, access to 6-aminoperhydro-1,4-Diazepines becomes much easier and faster.
Francois Huet - One of the best experts on this subject based on the ideXlab platform.
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highly peri regio and diastereoselective 1 3 dipolar cycloaddition of mesitonitrile oxide to 1 7 dimethyl 2 3 dihydro 1h 1 4 Diazepines unexpected one step formation of a new triheterocyclic framework
New Journal of Chemistry, 2001Co-Authors: A Baouid, J.-p. Lavergne, Said Elhazazi, A Hasnaoui, Philippe Compain, Francois HuetAbstract:We report here an efficient one-step synthesis of new [1,2,4]oxadiazolo[4,5-d][1,4]Diazepines and [1,2,4]oxadiazolo[4,5-d][1,4]-diazepine-8-spiro-5′-isoxazolines by way of highly peri-, regio- and diastereoselective 1,3-dipolar cycloadditions of mesitonitrile oxide to 1,7-dimethyl-2,3-dihydro-1H-1,4-Diazepines. The structures were elucidated by spectral methods and X-ray crystallographic analysis. The regiochemistry of the cycloaddition is dictated by frontier orbital interactions.
J.-p. Lavergne - One of the best experts on this subject based on the ideXlab platform.
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highly peri regio and diastereoselective 1 3 dipolar cycloaddition of mesitonitrile oxide to 1 7 dimethyl 2 3 dihydro 1h 1 4 Diazepines unexpected one step formation of a new triheterocyclic framework
New Journal of Chemistry, 2001Co-Authors: A Baouid, J.-p. Lavergne, Said Elhazazi, A Hasnaoui, Philippe Compain, Francois HuetAbstract:We report here an efficient one-step synthesis of new [1,2,4]oxadiazolo[4,5-d][1,4]Diazepines and [1,2,4]oxadiazolo[4,5-d][1,4]-diazepine-8-spiro-5′-isoxazolines by way of highly peri-, regio- and diastereoselective 1,3-dipolar cycloadditions of mesitonitrile oxide to 1,7-dimethyl-2,3-dihydro-1H-1,4-Diazepines. The structures were elucidated by spectral methods and X-ray crystallographic analysis. The regiochemistry of the cycloaddition is dictated by frontier orbital interactions.
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1,3-Dipolar Cycloaddition with the 5,7-Dimethyl-1,2-diazepine
Synthetic Communications, 1994Co-Authors: M. El Messaoudi, Aissa Hasnaoui, J.-p. LavergneAbstract:Abstract We report here a one-step synthesis of the bis-[1,2,4] oxadiazolino [4,5-b; 5,4-g] [1,2]-Diazepines 3,5 and [1,2,4] triazolino [4,5-b]-pyrazolino [4,5-f] [1,2]-diazepine, 7 by 1,3-dipolar cycloaddition of nitrile oxides and nitrilimines with the 1,2-diazepine 1.
Ales Reisinger - One of the best experts on this subject based on the ideXlab platform.
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4-Pyridylnitrene and 2-pyrazinylcarbene
2013Co-Authors: Ales Reisinger, Curt Wentrup, David Kvaskoff, Beilstein Org J. ChemAbstract:carbene–nitrene interconversion; Diazepines; flash vacuum thermolysis; matrix photochemistry; nitrile ylides; reactive intermediate
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1H-1,3-Diazepines, 5H-1,3-Diazepines, 1,3-diazepinones, and 2,4-diazabicyclo[3.2.0]heptenes.
Organic & biomolecular chemistry, 2004Co-Authors: Ales Reisinger, Paul V. Bernhardt, Rainer Koch, Curt WentrupAbstract:Tetrazolo[1,5-a]pyridines/2-azidopyridines 1 undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes 3, which react with alcohols to afford 2-alkoxy-1H-1,3-Diazepines 4 (5), with secondary amines to 2-dialkylamino-5H-1,3-Diazepines 16, sometimes via isolable 2-dialkylamino-1H-1,3-Diazepines 15, and with water to 1,3-diazepin-2-ones 19. The latter are also obtained by elimination of isobutene or propene from 2-tert-butoxy- or 2-isopropoxy-1H-1,3-Diazepines 4 or 5. 1,3-Diazepin-2-one 22B and 1,3-diazepin-4-one 24 were obtained from hydrolysis of the corresponding 4-chloroDiazepines. Diazepinones 19 undergo photochemical ring closure to diazabicycloheptenones 25 in high yields. The 2-alkoxy-1H-1,3-Diazepines 4 and 5 interconvert by rapid proton exchange between positions N1 and N3. The free energies of activation for the proton exchange were measured by the Forsen–Hoffman method as ΔG‡298 = 16.2 ± 0.6 kcal mol−1 as an average for 4a–c in CD2Cl2, acetone-d6, and methanol-d4, and 14.1 ± 0.6 kcal mol−1 for 4c in acetone/D2O. The structures of 2-methoxy-5,6-bis(trifluoromethyl)-1H-1,3-diazepine 4k, 1,2-dihydro-4-diethylamino-5H-1,3-diazepin-2-one 22bB, and diazabicycloheptanone 26 were determined by X-ray crystallography. The former represents the first reported X-ray crystal structure of any monocyclic N-unsubstituted 1H-azepine.
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Synthesis of 1,3-Diazepines and ring contraction to cyanopyrroles.
Organic & biomolecular chemistry, 2003Co-Authors: Ales Reisinger, Paul V. Bernhardt, Curt WentrupAbstract:Several tetrazolo[1,5-a]pyridines/2-azidopyridines undergo photochemical nitrogen elimination and ring expansion to 1,3-diazacyclohepta-1,2,4,6-tetraenes (7,10,13,16,19,22) as well as ring cleavage to cyanovinylketenimines (8,17,20b) in low temperature Ar matrices. 6,8-Dichlorotetrazolo[1,5-a]pyridine/2-azido-3,5-dichloropridine 6 undergoes ready exchange of the chlorine in position 8 (3) with ROH/RONa. 8-Chloro-6-trifluoromethyltetrazolo[1,5-a]pyridine 15 undergoes solvolysis of the CF3 group to afford 8-chloro-6-methoxycarbonyltetrazolo[1,5-a]pyridine 18. Several tetrazolopyridines/2-azidopyridines afford 1H- or 5H-1,3-Diazepines in good yields on photolysis in the presence of alcohols or amines (11,14,23,25). 5-Chlorotetrazolo[1,5-a]pyridines/2-azido-6-chloropyridines 21 and 38 undergo a rearrangement to 1H- and 3H-3-cyanopyrroles 27 and 45, respectively. The mechanism of this rearrangement was investigated by 15N-labelling and takes place via transient 1,3-Diazepines. The structures of 6,8-dichloro-tetrazolo[1,5-a]pyridine 6T, 6-chloro-8-ethoxytetrazolo[1,5-a]pyridine 9Tb, dipyrrolylmethane 28, and 2-isopropoxy-4-dimethylamino-5H-1,3-diazepine 25b were determined by X-ray crystallography. In the latter case, this represents the first reported X-ray crystal structure of a 5H-1,3-diazepine.