- Facile Access to 1,4-Disubstituted Pyrrolo[1,2- a ]pyrazines from α-Aminoacetonitriles
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An efficient and practical synthetic protocol for the synthesis of 1,4-disubstituted pyrrolo[1,2- a ]pyrazine derivatives is described that originates from α-substituted pyrroloacetonitriles which, in turn, are readily available from aryl and alkyl aldehydes. The α-pyrroloacetonitriles were subjected to a Friedel-Crafts acylation with methyl chlorooxoacetate followed by reduction of the nitrile group under Pd-catalyzed hydrogenation conditions and finally aromatization with DDQ leading to the desired pyrrolo[1,2- a ]pyrazine derivatives. This method was generalized and successfully applied to various aryl, heteroaryl, and alkyl substrates. The developed protocol provides direct and convenient access to 1,4-disubstituted ring systems in moderate to good overall yields (51-68percent) without the need for purification of the intermediates. Further functionalization via the stepwise halogenation (bromination, iodination) and nitration was also demonstrated. In addition, the potential of the ester functionality for elaboration was demonstrated by manipulating into heterocyclic ring systems, exemplified by conversion into benzoxazole derivatives.
- Basha, Mushkin,Belema, Makonen,Dhar, T. G. Murali,Gupta, Anuradha,Gupta, Arun Kumar,Indasi, Gopi Kumar,Karmakar, Ananta,Mathur, Arvind,Meanwell, Nicholas A.,Ramalingam, Sridharan,Rampulla, Richard
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supporting information
p. 441 - 449
(2020/01/23)
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- Titanium-Catalyzed Cyano-Borrowing Reaction for the Direct Amination of Cyanohydrins with Ammonia
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α-Aminonitrile was an important building block in natural products and key intermedia in organic chemistry. Herein, the direct amination of cyanohydrins with the partner of ammonia to synthesis N-unprotected α-aminonitriles is developed. The reaction proceeds via titanium-catalyzed cyano-borrowing reaction, which features high atom economy and simple operation. A broad range of ketone or aldehyde cyanohydrins was tolerated with ammonia, and the N-unprotected α-aminonitriles were synthesis with moderate to high yields under mild reaction conditions.
- Li, Qing-Hua,Li, Zhao-Feng,Tao, Jing,Li, Wan-Fang,Ren, Li-Qing,Li, Qian,Peng, Yun-Gui,Liu, Tang-Lin
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supporting information
p. 8429 - 8433
(2019/10/14)
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- A Sustainable, Semi-Continuous Flow Synthesis of Hydantoins
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Hydantoins are an important class of heterocycles with applications in pharmacy, agriculture, and as intermediates in organic synthesis. Traditional synthetic procedures to access hydantoins are target oriented with multiple synthetic steps and often use reagents that are not commercially available or sustainable. Herein, an efficient process is described for accessing hydantoins starting from commercially available amines using consecutive gas–liquid transformations (oxygen, carbon dioxide). This semi-continuous process produced ten benzylic/aliphatic hydantoins in good overall yields (52–84 %).
- Vukeli?, Stella,Koksch, Beate,Seeberger, Peter H.,Gilmore, Kerry
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supporting information
p. 13451 - 13454
(2016/09/13)
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- Nitrilases, nucleic acids encoding them and methods for making and using them
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The invention relates to nitrilases and to nucleic acids encoding the nitrilases. In addition methods of designing new nitrilases and method of use thereof are also provided. The nitrilases have increased activity and stability at increased pH and temperature.
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Page/Page column 89; 90
(2016/01/09)
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- Flow synthesis of fluorinated α-amino acids
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Fluorinated α-amino acids are versatile compounds that are used for many purposes in medicinal and biochemistry. However, their synthesis remains a significant hurdle, often requiring multiple steps, multiple protecting groups, and/or the use of highly toxic reagents. These challenges have limited the application of fluorinated α-amino acids. A convenient, protecting-group-free and semi-continuous process for the synthesis of racemic fluorinated α-amino acids from fluorinated amines is described. Following a singlet-oxygen-driven photooxidative cyanation, an acid-mediated hydrolysis of the intermediate α-amino nitrile yields the desired α-amino acid. Aliphatic, benzylic, and homobenzylic residues with different fluorination degrees are tolerated, providing good overall yields (50-67?%). This semi-continuous process is particularly advantageous for an aliphatic amine, the intermediate α-amino nitrile of which decomposes upon isolation. An efficient, semi-continuous, and protecting-group-free method for the synthesis of fluorinated α-amino acids from the corresponding amines has been developed. A low temperature photooxidative cyanation of benzylic and aliphatic amines provided α-amino nitriles with varying fluorination patterns. These unstable intermediates were trapped with an acid-mediated hydrolysis with good overall yields.
- Vukelic, Stella,Ushakov, Dmitry B.,Gilmore, Kerry,Koksch, Beate,Seeberger, Peter H.
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supporting information
p. 3036 - 3039
(2015/05/13)
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- Pyrroles and indolizidines from deprotonated α-(alkylideneamino) nitriles
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Their ready availability from simple starting materials in only two synthetic steps and their versatility as building blocks for the construction of highly substituted amines and N-heterocycles renders α-(alkylideneamino) nitriles useful synthetic intermediates. Herein, short syntheses of tri- and tetrasubstituted pyrroles including the northern half of the HMG-CoA reductase inhibitor atorvastatin as well as an access to 3-substituted indolizidines will be described. Georg Thieme Verlag Stuttgart - New York.
- Schaefer, Ines,Opatz, Till
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experimental part
p. 1691 - 1704
(2011/07/29)
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- Cyclocondensation of α-aminonitriles and enones: A short access to 3,4-dihydro-2H-pyrrole 2-carbonitriles and 2,3,5-trisubstituted pyrroles
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(Chemical Equation Presented) The reaction of α,β-unsaturated carbonyl compounds with aminoacetonitrile hydrochloride furnishes 3,5-disubstituted 3,4-dihydro-2H-pyrrole-2-carbonitriles in a one-pot reaction sequence. While these products can serve as starting materials for the preparation of polysubstituted pyrrolizidines, they are kinetically stable against the base-induced elimination of HCN. In contrast, their 2-substituted analogues obtained from α-substituted α-aminonitriles can be readily converted to the corresponding 2,3,5-trisubstituted pyrroles under microwave irradiation. The key step presumably involves the thermal electrocyclization of a stabilized 2-azapentadienyl anion formed by condensation of the reactants and subsequent deprotonation.
- Bergner, Ines,Wiebe, Christine,Meyer, Nino,Opatz, Till
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supporting information; experimental part
p. 8243 - 8253
(2010/02/17)
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- Chemoenzymatic approaches to the dynamic kinetic asymmetric synthesis of aromatic amino acids
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Enzymatic approaches for the production of amino acids by nitrilases are described. Dynamic kinetic asymmetric synthesis conditions were established for the aromatic aminonitriles, phenylglycinonitrile and 4- fluorophenylglycinonitrile, at high pH to produce the corresponding amino acid products in high enantiomeric excess. N-Acylation of aromatic aminonitriles led to spontaneous racemization at pH 8, allowing preferential enzymatic hydrolysis of the (R)-enantiomer to afford the product N-acylamino acids in up to 99% enantiomeric excess (ee).
- Chaplin, Jennifer A.,Levin, Michael D.,Morgan, Brian,Farid, Nancy,Li, Jen,Zhu, Zuolin,McQuaid, Jeff,Nicholson, Lawrence W.,Rand, Cynthia A.,Burk, Mark J.
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p. 2793 - 2796
(2007/10/03)
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- A facile synthesis of substituted phenylglycines
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A convenient scaleable process for the preparation of substituted phenylglycines 2 by a modified Strecker reaction is described. Bisulfite- mediated addition of benzylamine and cyanide anion to substituted benzaldehydes 3 gave the aminonitriles 4 which were hydrolysed in two steps to the N-protected amino acid 1. Debenzylation using catalytic transfer hydrogenation gave the title compounds in good yield.
- Davies, Antony J.,Ashwood, Michael S.,Cottrell, Ian F.
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p. 1095 - 1102
(2007/10/03)
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