- Scandium(III) Triflate Catalyzed Direct Synthesis of N-Unprotected Ketimines
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N-Unprotected ketimines are useful substrates and intermediates for synthesizing valuable nitrogen-containing compounds, but their potential applicability is limited by the available synthetic methods. To address this issue, we report a scandium(III) triflate catalyzed direct synthesis of N-unprotected ketimines. Using commercially available reagents and Lewis acid catalysts, ketones were directly transformed into the corresponding N-unprotected ketimines in high yields with broad functional group tolerance, even in multigram scales. The reactions were readily applicable for one-pot synthesis of important compounds such as a glycine Schiff base without isolation of N-unprotected ketimine intermediates. Preliminary mechanistic studies to clarify the reaction mechanism are also described.
- Hirazawa, Yoshinobu,Kadota, Tetsuya,Kondo, Yuta,Morimoto, Hiroyuki,Morisaki, Kazuhiro,Ohshima, Takashi
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supporting information
p. 120 - 125
(2020/02/20)
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- Cross-Coupling of Alkyl Redox-Active Esters with Benzophenone Imines: Tandem Photoredox and Copper Catalysis
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Alkyl amines are an important class of organic compounds in medicinal and materials chemistry. Until now very have been very few methods for the synthesis of alkyl amines by metal-catalyzed cross-coupling of alkyl electrophiles with nitrogen nucleophiles. Described here is an approach to employ tandem photoredox and copper catalysis to enable the cross-coupling of alkyl N-hydroxyphthalimide esters, readily derived from alkyl carboxylic acids, with benzophenone-derived imines. Hydrolysis of the coupling products furnish alkylated primary amines. Primary, secondary, and tertiary alkyl groups can be transferred, and the coupling tolerates a diverse set of functional groups. The method allows rapid functionalization of natural products and drugs, and can be used to expedite syntheses of pharmaceuticals from readily available chemical feedstocks.
- Mao, Runze,Balon, Jonathan,Hu, Xile
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supporting information
p. 9501 - 9504
(2018/07/29)
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- Hydrogen bond directed aerobic oxidation of amines via photoredox catalysis
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An application of H-bonding interactions for directing the α-C-H oxidation of amines to amides and amino-ketones catalyzed by an organic photocatalyst is reported. The high efficiency of this method is demonstrated by the aerobic oxidation of pyrrolidines, diarylamines and benzylamines bearing urea groups with high yields and a wide substrate scope.
- Wang, Hongyu,Man, Yunquan,Wang, Kaiye,Wan, Xiuyan,Tong, Lili,Li, Na,Tang, Bo
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supporting information
p. 10989 - 10992
(2018/10/08)
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- Manganese-catalyzed dehydrogenative [4+2] annulation of N-H imines and alkynes by C-H/N-H activation
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Described herein is a manganese-catalyzed dehydrogenative [4+2] annulation of N-H imines and alkynes, a reaction providing highly atom-economical access to diverse isoquinolines. This transformation represents the first example of manganese-catalyzed C-H activation of imines; the stoichiometric variant of the cyclomanganation was reported in 1971. The redox neutral reaction produces H2 as the major byproduct and eliminates the need for any oxidants, external ligands, or additives, thus standing out from known isoquinoline synthesis by transition-metal-catalyzed C-H activation. Mechanistic studies revealed the five-membered manganacycle and manganese hydride species as key reaction intermediates in the catalytic cycle.
- He, Ruoyu,Huang, Zhi-Tang,Zheng, Qi-Yu,Wang, Congyang
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supporting information
p. 4950 - 4953
(2014/05/20)
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- Pd-catalyzed enantioselective C-H iodination: Asymmetric synthesis of chiral diarylmethylamines
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An enantioselective C-H iodination reaction using a mono-N-benzoyl- protected amino acid has been developed for the synthesis of chiral diarylmethylamines. The reaction uses iodine as the sole oxidant and proceeds at ambient temperature and under air.
- Chu, Ling,Wang, Xiao-Chen,Moore, Curtis E.,Rheingold, Arnold L.,Yu, Jin-Quan
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supporting information
p. 16344 - 16347
(2013/12/04)
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- Serine and threonine Schiff base esters react with β-anomeric peracetates in the presence of BF3·Et2O to produce β-glycosides
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Improved procedures are reported for the glycosylation of L-serine and L-threonine utilizing activated Schiff base glycosyl acceptors, which are less expensive and more efficient alternatives to published methods. L-serine or L-threonine benzyl ester hydrochloride salts were reacted with the diarylketimine bis-(4-methoxyphenyl)-methanimine in CH3CN at rt to form the more nucleophilic Schiff bases 3a and 3b in excellent yield. These Schiff bases exhibited ring-chain tautomerism in CDCl3 as shown by 1H NMR. Schiff bases 3a and 3b, acting as glycosyl acceptors, reacted at rt with simple sugar peracetate donors with BF3·OEt 2 promotion to provide the corresponding L-serine and L-threonine O-linked glycosides in excellent yields and purities. The dipeptide ester Schiff base Ar2C = N-Ser-Val-OCH3 3e also reacted to provide β-glycosides in excellent yields, and without epimerization. With microwave irradiation the reactions were complete in 2 to 5 min. To investigate this reaction further, classical AgOTf-promoted Koenigs-Knorr reaction of D-glucopyranosyl, lactosyl, and maltosyl bromides were examined, providing the β-glycosides with yields ranging from 35% to 68%. The difference in reactivity between α- and β-carbohydrate peracetate donors was remarkable. The less configurationally stable D-xylopyranosyl tetra-acetate (a pentose) showed no selectivity (αvsβ-configuration) toward the Schiff bases. Copyright Taylor & Francis Group, LLC.
- Keyari, Charles M.,Polt, Robin
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experimental part
p. 181 - 206
(2011/04/23)
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- IMPROVED METHOD FOR MAKING AMINO ACID CLYCOSIDES AND GLYCOPEPTIDES
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The invention relates to an improved method of preparing amino glycosides and glycopeptides. The method involves reacting an diarylketimine with an amino acid having a hydroxal side chain to produce an imino-bound intermediate compound. This intermediate is then reacted with an acetylated sugar residue under suitable conditions to yield amino glycoside. The synthetic amino glycoside may be incorporated into a peptide chain under conditions compatible with standard glycopeptide synthesis reactions.
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Page/Page column 8
(2010/11/27)
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- Synthesis of substituted benzhydrylamines
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The synthesis of para di- and monosubstituted benzhydrylamines by addition of Grignard reagents to benzonitriles and subsequent reduction, is evaluated and discussed. The reduction step with sodium borohydride allows simple handling and mild conditions. An optimized synthesis of 4,4'-dimethoxybenzhydrylamine by this method is disclosed.
- Dejaegher,Mangelinckx,De Kimpe
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p. 113 - 115
(2007/10/03)
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