- The thermal isomerisation benzoazetine - 6-methylene-2,4-cyclohexadien-1-imine: A photoelectron investigation
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The flash vacuum thermolyses of 1,2,3,4-tetrahydroquinoline 3, o-aminobenzylalcohol 4 and o-aminobenzylamine 5 were performed at temperatures from 923 to 1273 K and monitored by photoelectron spectrometry. While thermolyses at 923-1073 K led to the until now undescribed benzoazetine 2a, 6-methylene-2,4- cyclohexadien-1-imine 1a was obtained at 1173-1273 K.
- Pfister-Guillouzo, Genevieve,Gracian, Francoise,Senio, Anna,Letulle, Marguerite,Ripoll, Jean-Louis
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- Regioselective Synthesis of C-3-Functionalized Quinolines via Hetero-Diels-Alder Cycloaddition of Azadienes with Terminal Alkynes
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A highly efficient metal and protection-free approach for the regioselective synthesis of C-3-functionalized quinolines from azadienes (in situ generated from 2-aminobenzyl alcohol) and terminal alkynes through [4 + 2] cycloaddition has been developed. An unprecedented reaction of 2-aminobenzyl alcohol with 1,3- and 1,4-diethynylbenzene provided the C-3 tolylquinolines via [4 + 2] HDA and oxidative decarboxylation. The -NH2 group directed mechanistic approach was well supported by the control experiments and deuterium-labeling studies and by isolating the azadiene intermediate. The reactivity and selectivity of unprotected azadiene in metal-free base-assisted hetero-Diels-Alder reaction is exploited to quickly assemble an important class of C-3-functionalized quinolines, which are difficult to access.
- Saunthwal, Rakesh K.,Patel, Monika,Verma, Akhilesh K.
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p. 6563 - 6572
(2016/08/16)
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- Metal- and Protection-Free [4 + 2] Cycloadditions of Alkynes with Azadienes: Assembly of Functionalized Quinolines
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A base promoted, protection-free, and regioselective synthesis of highly functionalized quinolines via [4 + 2] cycloaddition of azadienes (generated in situ from o-aminobenzyl alcohol) with internal alkynes has been discovered. The reaction tolerates a wide variety of functional groups which has been successfully extended with diynes, (2-aminopyridin-3-yl)methanol, and 1,4-bis(phenylethynyl)benzene to afford (Z)-phenyl-2-styrylquinolines, phenylnaphthyridine, and alkyne-substituted quinolines, respectively. The proposed mechanism and significant role of the solvent were well supported by isolating the azadiene intermediate and deuterium-labeling studies.
- Saunthwal, Rakesh K.,Patel, Monika,Verma, Akhilesh K.
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p. 2200 - 2203
(2016/06/01)
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- Application of photoelectron spectroscopy to molecular properties, 57[≠] UV photoelectron spectroscopy studies of the products of thermal extrusion of sulfur dioxide from benzosultams
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An aza-ortho-xylylene system is produced by thermal degradation of N- alkylbenzosultam, which can be directly studied by coupling the system to a UV/photoelectron spectrometer. These thermodynamically unstable xylylene derivatives rearrange to give aldimine by a [1,5] hydrogen shift.
- Chrostowska, Anna,Gracian, Francoise,Sotiropoulos, Jean-Marc,Pfister-Guillouzo, Genevieve,Wojciechowski, Krzysztof
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p. 313 - 318
(2007/10/03)
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- Intramolecular Hydrogen Transfer in (2-Aminophenyl)carbene and 2-Tolylnitrene. Matrix Isolation of 6-Methylene-2,4-cyclohexadien-1-imine
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Flash vacuum pyrolysis (FVP) or matrix photolysis of 2-(diazomethyl)phenylamine, 1-azido-2-methylbenzene (2-tolyl azide), o-aminobenzyl alcohol, or 2-indolinone provide entries into the C7H7N hypersurface.The matrix-isolated (argon, 10 K) products have been characterized by IR and UV-vis spectroscopy in combination with high level (MP2/6-31G(d) and HF/6-31G(d,p)) ab-initio calculations.FVP (500-800 deg C) of the first three of these precursors produces high yields of E/Z-mixtures of 6-methylene-2,4-cyclohexadien-1-imine (o-iminoquinone methide), while the bicyclic isomer benzoazetine is not formed under these conditions.FVP of 2-tolyl azide at very high temperatures (>900 deg C) leads to the formation of benzaldimine and benzonitrile.Photolysis of the matrix-isolated precursors allows one to selectively generate the E- and Z-isomer of the iminoquinone methide as well as benzoazetine.In addition, 2-tolylnitrene and 1-aza-3-methyl-1,2,4,6-cycloheptatetraene are produced as intermediates in the photolysis of 2-tolyl azide.The nitrene is thermally stable up to 80 K (in xenon matrix), although the hydrogen migration to give (E)-o-iminoquinone methide is calculated to be exothermic by 42 kcal/mol.Irradiation of 2-(diazomethyl)phenylamine directly yields the quinone methide while (o-aminophenyl)carbene, which is the most reasonable intermediate, is not observed.
- Morawietz, Jens,Sander, Wolfram,Traeubel, Michael
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p. 6368 - 6378
(2007/10/03)
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- The syntheses of 6-methylene-2,4-cyclohexadien-1-imine and related o-quinonoids by FVT of 1-hetero-1,2,3,4-tetrahydronaphthalenes
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Flash vacuum thermolysis (~ 1000 °C/10-5 hPa) of 1,2,3,4-tetrahydroquinoline chroman, and thiochroman led upon loss of ethylene (retro-Diels-Alder reaction) to the o-quinonoids 1-3. These reactive monomers were identified by IR-UV at -196 °C and/or MS/MS.
- Letulle,Guenot,Ripoll
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p. 2013 - 2016
(2007/10/02)
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