Selektive kohlenstoff-kohlenstoff-verknüpfungen mit nucleophilen thermolabilen methylcobalt-reagenzien

Kauffmann, Thomas; Hopp, G.; Laarmann, B.; Stegemann, D.; Wingbermühle, Dorothea

doi:10.1016/0040-4039(90)87021-q

“…As shown in Table 3, all these reactions proceeded efficiently to furnish the desired tetrahydroquinoxaline products in 71-99 % yields with d.r. values of 98:2-> 99:1, and 67-96 % ee (entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The substituents at the 2,3-positions of the quinoxalines influenced the enantioselectivity (entries 1-4).…”

Section: Methodsmentioning

confidence: 99%

A Highly cis‐Selective and Enantioselective Metal‐Free Hydrogenation of 2,3‐Disubstituted Quinoxalines

Zhang

¹

,

Du

²

2014

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A wide range of 2,3-disubstituted quinoxalines have been successfully hydrogenated with H2 using borane catalysts to produce the desired tetrahydroquinoxalines in 80-99% yields with excellent cis selectivity. Significantly, the asymmetric reaction employing chiral borane catalysts generated by the in situ hydroboration of chiral dienes with HB(C6F5)2 under mild reaction conditions has also been achieved with up to 96% ee, and represents the first catalytic asymmetric system to furnish optically active cis-2,3-disubstituted 1,2,3,4-tetrahydroquinoxalines.

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“…As shown in Table 3, all these reactions proceeded efficiently to furnish the desired tetrahydroquinoxaline products in 71-99 % yields with d.r. values of 98:2-> 99:1, and 67-96 % ee (entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The substituents at the 2,3-positions of the quinoxalines influenced the enantioselectivity (entries 1-4).…”

Section: Methodsmentioning

confidence: 99%

“…When 2-phenyl-3,5-dimethylquinoxaline was employed as a substrate, only 67 % ee was obtained (entry 5). In contrast, substituents at the 6-, 7-, and 8-positions gave much higher ee values (entries [6][7][8][9][10][11][12][13][14]. The absolute configuration of the compound 2 l was determined to be (2R,3S) by its X-ray structure (Figure 1).…”

Section: Methodsmentioning

confidence: 99%

“…[15b] These reactions went well to give trans-2 a as a major product ( Table 1, entries 1 and 2). Further lowering the temperature can obviously improve the cis selectivities (entries [3][4][5][6], and up to 98:2 d.r. was obtained at 60 8C using 3 b.…”

Section: Zhenhua Zhang and Haifeng Du*mentioning

confidence: 99%

“…[4] However, in sharp contrast, the reduction of 2,3substituted quinoxalines has been rarely reported. [5,6] For example, Deselms and Mosher reported a noncatalytic lithium aluminium hydride reduction of 2,3-dimethylquinoxaline to give a cis product in 1960 (Scheme 1). [5a] Gavin and coworkers described the reduction of 2,3-dimethyl-and 2,3diphenylquinoxaline with borane in THF solution (Scheme 1).…”

mentioning

confidence: 99%

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A Highly cis‐Selective and Enantioselective Metal‐Free Hydrogenation of 2,3‐Disubstituted Quinoxalines

Zhang

¹

,

Du

²

2014

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A wide range of 2,3-disubstituted quinoxalines have been successfully hydrogenated with H 2 using borane catalysts to produce the desired tetrahydroquinoxalines in 80-99 % yields with excellent cis selectivity. Significantly, the asymmetric reaction employing chiral borane catalysts generated by the in situ hydroboration of chiral dienes with HB(C 6 F 5 ) 2 under mild reaction conditions has also been achieved with up to 96 % ee, and represents the first catalytic asymmetric system to furnish optically active cis-2,3-disubstituted 1,2,3,4-tetrahydroquinoxalines.Tetrahydroquinoxalines are very useful moieties and present in a wide range of biologically and medicinally active compounds, and a lot of methods have been developed to access them. [1] The direct reduction of quinoxalines is one of the most efficient approaches among these methodologies. [2] In particular, the catalytic hydrogenation with H 2 as well as its asymmetric version has attracted attention and great advances have been made. [3] Since the first asymmetric hydrogenation of 2-methylquinoxaline with chiral rhodium catalysts reported by Murata and co-workers in 1987, [4a] a variety of chiral transition metal catalysts have been developed for the enantioselective hydrogenation of 2-substituted quinoxalines. [4] However, in sharp contrast, the reduction of 2,3substituted quinoxalines has been rarely reported. [5,6] For example, Deselms and Mosher reported a noncatalytic lithium aluminium hydride reduction of 2,3-dimethylquinoxaline to give a cis product in 1960 (Scheme 1). [5a] Gavin and coworkers described the reduction of 2,3-dimethyl-and 2,3diphenylquinoxaline with borane in THF solution (Scheme 1). [5b] Recently, Xu, Fan, and Xiao reported an iridiumcatalyzed transfer cis-selective hydrogenation of 2,3-dimethylquinoxaline (Scheme 1). [5c] Glorius and co-workers described a ruthenium/carbene-catalyzed cis-selective hydrogenation of 2,3-diphenyl-6-methylquinoxaline. In 2011, Fan and co-workers disclosed the first and the only asymmetric hydrogenation of 2,3-dialkylquinoxalines with chiral cationic ruthenium diamine catalysts to give the desired trans products with up to 99 % ee and 86:14 d.r. (Scheme 1). [5e] Therefore, the development of highly stereoselective hydrogenations of 2,3disubstituted quinoxalines under mild reaction conditions with a good substrate scope, especially the corresponding asymmetric reactions, still remains a challenge in the field of catalytic hydrogenation.The recently emerging frustrated Lewis pair (FLP) chemistry provides a breakthrough approach for metal-free hydrogenation with molecular H 2 since catalytic hydrogenation has long been dominated by transition-metal catalysis. [7][8][9] A wide range of unsaturated compounds have proven to be effective substrates for the FLP-catalyzed hydrogenations. [9,10] Significantly, some promising advances have also been made for FLP-catalyzed asymmetric reactions, [11,12] but the asymmetric hydrogenation of silyl enol ethers is the only example to proceed with more than 90 % ee. ...

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Formation of Alkenes by Metal‐promoted Coupling Reactions

Larock

¹

,

Zeni

²

2018

Comprehensive Organic Transformations

0

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Alkali Metal Reagents Grignard Reagents Boron Reagents Aluminum Reagents Indium Reagents Thallium Reagents Silicon Reagents Germanium Reagents Tin Reagents Bismuth Reagents Arsenic Reagents Sulfur Reagents Selenium Reagents Tellurium Reagents Titanium Reagents Zirconium Reagents Vanadium Reagents Molybdenum Reagents Manganese Reagents Iron Reagents Ruthenium Reagents Cobalt Reagents Nickel Reagents Palladium Reagents Copper Reagents Silver Reagents Zinc Reagents Mercury Reagents Olefin Metathesis

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Selektive kohlenstoff-kohlenstoff-verknüpfungen mit nucleophilen thermolabilen methylcobalt-reagenzien

Cited by 27 publications

References 3 publications

A Highly cis‐Selective and Enantioselective Metal‐Free Hydrogenation of 2,3‐Disubstituted Quinoxalines

A Highly cis‐Selective and Enantioselective Metal‐Free Hydrogenation of 2,3‐Disubstituted Quinoxalines

A Highly cis‐Selective and Enantioselective Metal‐Free Hydrogenation of 2,3‐Disubstituted Quinoxalines

Formation of Alkenes by Metal‐promoted Coupling Reactions

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