- Continuous-flow oxidative cyanation of primary and secondary amines using singlet oxygen
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Primary and secondary amines can be rapidly and quantitatively oxidized to the corresponding imines by singlet oxygen. This reactive form of oxygen was produced using a variable-temperature continuous-flow LED-photoreactor with a catalytic amount of tetraphenylporphyrin as the sensitizer. α- Aminonitriles were obtained in good to excellent yields when trimethylsilyl cyanide served as an insitu imine trap. At 25°C, primary amines were found to undergo oxidative coupling prior to cyanide addition and yielded secondary α-aminonitriles. Primary α-aminonitriles were synthesized from the corresponding primary amines for the first time, by an oxidative Strecker reaction at -50 °C. This atom-economic and protecting-group-free pathway provides a route to racemic amino acids, which was exemplified by the synthesis of tert-leucine hydrochloride from neopentylamine. The mild synthesis of imines paves the way to aminonitriles and amino acids. Aerobic oxidation of primary and secondary amines in a continuous photoreactor with singlet oxygen generated insitu led to the rapid formation of imines, which were quantitatively trapped as α-aminonitriles (see scheme; TMS=trimethylsilyl). Benzylic and primary α-aminonitriles, precursors for amino acids, could be efficiently produced in three minutes.
- Ushakov, Dmitry B.,Gilmore, Kerry,Kopetzki, Daniel,McQuade, D. Tyler,Seeberger, Peter H.
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supporting information
p. 557 - 561
(2014/01/23)
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- Synthesis of alkaloids by stevens rearrangement of nitrile-stabilized ammonium ylides: (±)-laudanosine, (±)-laudanidine, (±)-armepavine, (±)-7-methoxycryptopleurine, and (±)-xylopinine
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The Stevens rearrangement of nitrile-stabilized ammonium ylides in conjunction with the reductive removal of the nitrile function permits the facile construction of α-branched amines from α-aminonitriles. We employed this reaction sequence for the preparation of (±)-laudanosine, (±)-laudanidine and (±)-armepavine, (±)-7- methoxycryptopleurine, and (±)-xylopinine from two closely related and readily accessible bicyclic α-aminonitriles. The final products were obtained in high to almost quantitative yields (71-98%) from the quaternary ammonium salts obtained by N-alkylation of these starting materials.
- Orejarena Pacheco, Julio Cesar,Lahm, Günther,Opatz, Till
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p. 4985 - 4992
(2013/06/27)
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- A new and efficient synthesis of derivatives of octahydro-4H-pyrrolo[1,2-c] pyrido[1′,2′-a]imidazole
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When diethyl malonate was added to a solution of Δ1- piperideine, generated in situ by oxidative desamination and decarboxylation of L-lysine by N-bromosuccinimide (NBS), formation of the unexpected tricyclic compound 6 (4-diethylmalonyl-octahydro-4H-pyrrolo[1,2-c]pyrido[1′, 2′-a]imidazole)was observed. The structure of 6 was deduced from analysis of its spectroscopic data and was confirmed both by chemical degradation and by total synthesis. We proved that 3-bromo-1-piperideine was implicated in its formation. Moreover, based on this feature, a new and efficient synthesis of 6 was developed. The elaborated pathway was adapted to access derivatives related to 6 that differed in their C-4 substituent. A new and efficient synthesis of derivatives of the tricyclic heterocycle A from lysine is described. A mechanism involving 3-halopiperideines as intermediates and based on a ring contraction followed by Michael reaction is proposed and tested. Copyright
- Rouchaud, Anne,Braekman, Jean-Claude
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p. 2346 - 2353
(2011/06/22)
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- Cyclization via carbolithiation of α-amino alkyllithium reagents
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(Chemical Equation Presented) We report a new route to tertiary α-amino stereocenters by sequential alkylation of α-amino nitriles followed by reductive lithiation of the nitrile and cycllzation onto an alkene. Reductive lithiation of α-amino nitriles usi
- Bahde, Robert J.,Rychnovsky, Scott D.
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supporting information; experimental part
p. 4017 - 4020
(2009/06/18)
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- Experimental Studies of the Anomeric Effect. Part VI. Ring Inversion Equilibria in Cyclohexane, Tetrahydropyran and Piperidine Rings Substituted by a Carbomethoxy or a Cyano Group.
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The ring inversion equilibrium in carbomethoxycyclohexane is compared with those in 2-carbomethoxytetrahydropyran and 2-carbomethoxypiperidine through a variable temperature nmr study of the positions of equilibria.The derived ΔH0ae values (kcal mol-1) of -1.24 (cyclohexane), -1.69 (tetrahydropyran) and -0.54 (piperidine) can be rationalised in terms of competition between steric effects and endo-anomeric effects of the ring heteroatom.Variable temperature studies have also given ΔH0ae values (kcal mol-1) for ring inversions in cyanocylohexane, 2-cyanotetrahydropyran and 2-cyanopiperidine as -0.18, +0.36 and +2.22.Steric effects are small for CN, and the trend in ΔH0 values is consistent with the expected increase in stabilising endo-anomeric effect along the series C, O, N.
- Booth, Harold,Dixon, J. Mark,Khedhair, Khedhair A.
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p. 6161 - 6174
(2007/10/02)
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- Process for preparing 2-acetyl-1-aza-1-cycloalkenes useful as flavor components for bread and rice
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Straightforvard and inexpensive syntheses of 2-acetyl-1-aza-1-cycloalkenes usefull as bread and rice flavor components, i.e. 2-acetyl-1,4,5,6-tetrahydropyridine and 2-acetyl-1-pyrroline, respectively, comprise the following steps : oxidation of cyclic amines to cyclic imines; subsequent cyanation of cyclic amines to 2-cyano-1-azacycloalkanes ; oxidation of 2-cyano-1-azacycloalkanes to 2-cyano-1-aza-1-cycloalkenes; synthesis of 2-acetyl-1-aza-1-cycloalkenes by a Grignard reaction. These syntheses give rise to the title compounds, free of side products, in a way easily amenable to industrial production.
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- HYPERVALENT IODINE OXIDATION OF AMINES USING IODOSOBENZENE: SYNTHESIS OF NITRILES, KETONES AND LACTAMS
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Primary aliphatic amines on oxidation with iodosobenzene in CH2Cl2 or H2O yield the corresponding nitriles, while primary cycloalkylamines give the corresponding cyclic ketones.Lactams are obtained by the oxidation of cyclic amines. (S)(-) Nicotine (15) is oxidized to (+/-)-cotinine (16).The intermediary imine involved in these processes was trapped in the case of piperidine as the α-aminonitrile.
- Moriarty, Robert M.,Vaid, Radhe K.,Duncan, Michael P.,Ochiai, Masahito,Inenaga, Minako,Nagao, Yoshimitsu
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p. 6913 - 6916
(2007/10/02)
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- TITANIUM(III) INDUCED TRANSFORMATIONS OF N,N-DISUBSTITUTED HYDROXYLAMINES TO IMINES AND SECONDARY AMINES
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The reaction of N,N-disubstituted hydroxylamines with anhydrous TiCl3 gives the corresponding imines, while that with aqueous TiCl3 gives secondary amines.
- Murahashi, Shun-Ichi,Kodera, Yoichi
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p. 4633 - 4636
(2007/10/02)
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- OXYDATION OF SECONDARY AMINES TO α-CYANOAMINES
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The dehydrogenation of secondary amines with phenylseleninic anhydride or acid under mild conditions in the presence of either sodium cyanide or trimethylsilylcyanide gives good yields of α-cyanoamines.These compounds can be regarded as protected imines, or as a source of α-amino-acids.
- Barton, Derek H. R.,Billion, Annick,Boivin, Jean
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p. 1229 - 1232
(2007/10/02)
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