- Chiral zinc amidate catalyzed additions of diethylzinc to aldehydes
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A series of bifunctional spiro ligands bearing “carboxamide–phosphine oxide” groups and ethylzinc carboxamidates from these ligands as catalysts for Et2Zn additions to aldehydes were reported. Excellent yields were obtained with moderate ee′s in Et2Zn additions to benzaldehyde derivatives, implying effectiveness of our newly designed catalytic structures as well as mediocre stereocontrol by these chiral ligands. Possible transition states were suggested based on the crystal structures of two ligands.
- Zhang, Jinxia,Li, Shasha,Zheng, Xinxin,Li, Hongjie,Jiao, Peng
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supporting information
p. 1913 - 1917
(2019/06/24)
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- A catalytic system for the activation of diorganozinc reagents
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We report a novel catalytic system for the activation of diorganozinc reagents. We assumed that the nucleophilic activation of diethylzinc should be efficiently performed by simple alkali metal salts. Indeed, the combination of sodium salts and 15-crown-5 significantly accelerates the rate of diethylzinc addition to benzaldehyde under mild conditions. The activity of the catalytic system strongly depends on the nature of the anion, decreasing in the order I->Br->Cl->F-. Under the optimized reaction conditions, various aryl, hetero aryl, and aliphatic aldehydes were converted with diethylzinc and the corresponding product was obtained in excellent yields. The first X-ray absorption spectroscopy measurements on such type of reactions provide initial insights that support the proposed catalytic cycle and suggest the formation of a zincate complex.
- Werner, Thomas,Bauer, Matthias,Riahi, Abdol Majid,Schramm, Heiko
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p. 4876 - 4883
(2014/08/05)
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- New bifunctional organocatalysts based on (R,R)-cyclohexane-1,2-diamine for the asymmetric addition of nucleophiles to aldehydes
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The amide and sulfamide derivatives of (1R,2R)-N,N-diethylcyclohexane-1,2- diamine can serve as organocatalysts for addition of Me3SiCN and Et2Zn to aldehydes.
- Maleev,Gugkaeva,Tsaloev,Moskalenko,Khrustalev
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- Phosphonium salt catalyzed addition of diethylzinc to aldehydes
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The addition of diethylzinc to aromatic, heteroaromatic, and aliphatic aldehydes at room temperature is efficiently catalyzed by 1-7 mol% tetrabutylphosphonium chloride. The corresponding addition products are obtained in good to excellent yields of up to 99%. Moreover, polymer bond phosphonium salts can be used to catalyze this reaction with excellent recovery of the polymer bond catalyst up to three cycles. The application of chiral bifunctional phosphonium salts revealed a remarkable counter anion effect. Changing the anion, the activity of the tetrabutylphosphonium salt decreased in the order Cl- > Br- > I- ≈ TsO- > BF4- ≈ PF6-. However, the nature of the cation had also significant influence. Tetraalkyl-ammonium chlorides showed similar activity compared to phosphonium chlorides, while alkaline metal chlorides proved to be considerably less active. Georg Thieme Verlag Stuttgart.
- Werner, Thomas,Riahi, Abdol Majid,Schramm, Heiko
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experimental part
p. 3482 - 3490
(2011/12/04)
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- Synthesis, characterization, and structures of arylaluminum reagents and asymmetric arylation of aldehydes catalyzed by a titanium complex of an N-sulfonylated amino alcohol
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A series of phenylaluminum reagents AlPhxEt3-x(L) (x = 1-3) containing adduct ligand L [Et2O, THF, OPPh3, or 4-dimethylaminopyridine (DMAP)] were synthesized and characterized. NMR studies showed that AlPhx
- Zhou, Shuangliu,Chuang, Da-Wei,Chang, Shih-Ju,Gau, Han-Mou
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scheme or table
p. 1407 - 1412
(2009/12/01)
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- Chiral aryl pyridyl alcohols as enantioselective catalysts in the addition of diethylzinc to substituted benzaldehydes
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Chiral (5-aryl-10,10-dimethyl-6-aza-tricyclo[7.1.1.02,7]undeca- 2(7),3,5-trien-8-yl)-diphenyl-methanols were prepared from highly enantiopure (1R)-(+)-α-pinene (> 97% ee), and applied in the enantioselective addition of diethylzinc to substitut
- Chang, Tien-Chu,Chen, Chinpiao
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experimental part
p. 606 - 615
(2009/05/11)
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- Synthesis of 3-substituted indazoles and benzoisoxazoles via Pd-catalyzed cyclization reactions: application to the synthesis of nigellicine
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Syntheses of 3-substituted indazoles and benzoisoxazoles were efficiently accomplished with the aid of Pd-catalyzed intramolecular carbon-nitrogen and carbon-oxygen bond formations. The catalyst system described herein allows the cyclization to proceed under very mild conditions and thus could be applied to a wide range of substrates with acid- or base-sensitive functional groups. A total synthesis for the indazole ring-containing natural product nigellicine is also described.
- Inamoto, Kiyofumi,Katsuno, Mika,Yoshino, Takashi,Arai, Yukari,Hiroya, Kou,Sakamoto, Takao
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p. 2695 - 2711
(2007/10/03)
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- Convenient synthesis of a new class of chiral hydroxymethyl-dihydrooxazole ligands and their application in asymmetric addition of diethylzinc to aromatic aldehydes
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A number of chiral hydroxymethyl-substituted dihydrooxazoles were synthesized from D- or L-mandelic acid and amino alcohols. The chiral ligands thus obtained were tested as catalyst in the asymmetric addition of diethylzinc to aromatic aldehydes, and the
- Li, Zhi-Ting,Li, Xin-Sheng,Li, Liang-Chao,Xu, Dong-Cheng
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p. 545 - 549
(2007/10/03)
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- Synthesis and activity of 2-methyl-3-aminopropiophenones as centrally acting muscle relaxants
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Some novel 2-methyl-3-aminopropiophenones were synthesized and their centrally acting muscle relaxant activities were,evaluated for an inhibitory effect on the flexor reflex in rats. The structure-activity relationships are discussed. In this series 2-methyl-3-pyrrolidino-1-(4-trifluoromethylphenyl)-propan-1-one (28) showed significant centrally acting muscle relaxant activity. In addition, the activities of each enantiomer (28-(S) and (R)) were studied along with their acute toxicities. Compound 28-(R) was found to exhibit more potent activity and weaker acute toxicity than 28-(S). Accordingly, compound 28-(R) (NK433) is under development as a novel centrally acting muscle relaxant.
- Shiozawa,Narita,Izumi,Kurashige,Sakitama,Ishikawa
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