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Hatano, Manabu; Terada, Masahiro; Mikami, Kōichi

doi:10.1002/1521-3757(20010105)113:1<255::aid-ange255>3.3.co;2-i

Cited by 16 publications

(22 citation statements)

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“…[95] Da das Fluoridion ein guter Br¸ckenligand ist, kann man f¸r den Fall, dass sich Komplexe wie 74 bilden kˆnnen, hohe Selektivit‰ten erwarten. Dar¸ber hinaus schlug Duthaler [84] vor, dass das Silan durch ein verbr¸ckendes Fluoridion nucleophil aktiviert [98] 85 % ee (Schema 40). Mit einem aus TiF 4 und 2,2'-Dihydroxy-1,1'-binaphthyl (BINOL) hergestellten Katalysator erzielte man Enantioselektivit‰ten von bis zu 94 % (Schema 39).…”

Section: Asymmetrische Additionen An Aldehydeunclassified

Der Einfluss von Halogenidionen in der Übergangsmetallkatalyse

2002

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Section: Asymmetrische Additionen An Aldehydeunclassified

Der Einfluss von Halogenidionen in der Übergangsmetallkatalyse

2002

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“…In 1996, Ito developed a highly enantioselective catalyst system generated from Pd 2 (dba) 3 and chiral diarylphosphino ferrocene ligands that resulted in enantiomeric excesses of up to 95 %. Mikami also reported high enantioselectivity using modified BINAP derivatives in this palladium‐catalyzed cyclization. In his later research, phosphine‐oxazoline N,P‐ligands (Figure ) proved to be equally efficient .…”

Section: Introductionmentioning

confidence: 85%

Thiazole, Imidazole and Oxazoline Based N,P‐Ligands for Palladium‐Catalyzed Cycloisomerization of 1,6‐Enynes

Liu

Rabten

et al. 2016

Eur J Org Chem

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A series of N,P‐ligands were prepared and evaluated in the asymmetric palladium‐catalyzed cycloisomerization of allyl propargyl ether substrates. The reactivity and enantioselectivity of the reaction was shown to be highly dependent on the chiral skeleton of the ligand structures with ee's ranging from 22–99 %. The proton source had a significant impact on the enantioselectivity. The generation of palladium hydride from formic acid led to the highest ee. A selectivity model based on a proposed transition state was used to predict and explain the enantiomeric outcome of the reaction.

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“…After stirring for 3 h, NEt 3 (three drops) and AcOEt (20 mL) were added. [8] Here, Red-Al ¾ reduction at room temperature led to a 43:57 diastereomeric mixture of alcohol 8 and its diastereomer (85 %). aq.…”

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confidence: 96%

“…Lactams are a versatile motif in organic chemistry and when functionalized, lactams often either show biological activity themselves, or are important building blocks for biologically active molecules such as (þ)-a-allokainic acid, (þ)-a-kainic acid, [2] acromelic acid, [3] isopilocarpine, [4] and isocynometrine. [8] However, the number of lactam preparations reported involving the transition-metalcatalyzed cycloisomerization of enynes is limited. However, this method for the synthesis of enantiomerically pure and functionalized lactams requires that the chiral centers and functional groups must be assembled in advance.…”

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confidence: 99%

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Lei

Waldkirch

et al. 2002

Angew. Chem.

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The rising demand for chiral raw materials, intermediates, and active ingredients in pharmaceuticals, agrochemicals, food additives, and fragrances provides the impetus for rapid developments in chiral technology. [1] It remains a huge challenge for organic chemists to develop highly enantiose-lective reactions for the preparation of enantiomerically pure compounds in a cost-effective manner. Lactams are a versatile motif in organic chemistry and when functionalized, lactams often either show biological activity themselves, or are important building blocks for biologically active molecules such as (þ)-a-allokainic acid, (þ)-a-kainic acid, [2] acromelic acid, [3] isopilocarpine, [4] and isocynometrine. [5] Generally, lactams are synthesized by intramolecular CÀN bond formation. However, this method for the synthesis of enantiomerically pure and functionalized lactams requires that the chiral centers and functional groups must be assembled in advance. Therefore, methodology that allows enantioselective carbon± carbon bond formation for the generation of functionalized lactams without presetting the chiral centers will be a significant advance in synthetic organic chemistry.The transition-metal-catalyzed intramolecular Alder-enetype reactions of enynes are well-developed [6] and provide efficient entries to a variety of useful functionalized carbocyclic [7] and heterocyclic compounds. [8] However, the number of lactam preparations reported involving the transition-metalcatalyzed cycloisomerization of enynes is limited. In fact, the literature contains only a single example describing a palladium-catalyzed cycloisomerization of alkynyl N-acyl enamines. [9] Very recently, a mechanistically different palladium(ii)-catalyzed synthesis of a-alkylidene-g-butyrolactams was reported. [10] Previously, we have discovered a Rhcatalyzed cycloisomerization of enynes and developed its asymmetric version. [11] Although this was a substrate-and ligand-dependent reaction, up to 96 % ee was achieved. [11b] This led us to consider strategies for expanding the scope of the reaction as well as improving the enantioselectivity. We report herein the results of this effort: in an efficient, mild, and general route to synthesize a variety of lactams in high enantioselectivity using a catalyst derived from a commercially available metal precursor [{Rh(cod)Cl} 2 ] and the ligand binap. [12] Initially, the reaction was studied with unprotected enyne amides (Scheme 1, R 3 ¼ H) as the cycloisomerization substrates. However, none of the desired cyclization products were detected and the starting materials were recovered. The negative results may be because the trans-isomer of this type of unprotected enyne amide is dominant, which would be unfavorable for the cycloisomerization (Scheme 1). [13] There-ZUSCHRIFTEN 4708

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Cited by 16 publications

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Der Einfluss von Halogenidionen in der Übergangsmetallkatalyse

Der Einfluss von Halogenidionen in der Übergangsmetallkatalyse

Thiazole, Imidazole and Oxazoline Based N,P‐Ligands for Palladium‐Catalyzed Cycloisomerization of 1,6‐Enynes

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