E-don-gruppierungen organishcer verbindungen als bevorzugte angriffs= stellen für nucleophile, alkylierende übergangsmetallreagenzien; eine erste übersicht

Kauffmann, Thomas; Abel, Katharina; Bonrath, Werner; Kolb, Martina; Möller, T.; Pahde, Claudia; Raedeker, Susanne; Robert, Michael; Wensing, Michael; Wichmann, B.

doi:10.1016/s0040-4039(00)85208-9

Cited by 19 publications

(4 citation statements)

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“…86,223 A neighboring group effect was also identified for oxirane ringopening, with heteroatom-containing α-substituents favoring the reaction (Table 95, entries 10 and 11). 494 Note that reaction of Bu 3 MnLi with oxiranes furnishes the corresponding alkenes, a reaction not observed with the alkyl Cu(I) reagents. 495 Allyldimethylmanganates, prepared from Me 3 MnLi and Bu 3 (allyl)Sn, react better than Me 3 MnLi with epoxides (Table 96).…”

Section: Reactions Of Nu-homomaasmentioning

confidence: 98%

“…When aldehyde–ketone pairs were submitted to (Cl 2 CH) 3 MnLi in THF at 0 °C, the selective transfer of the Cl 2 CH group to the aldehyde was observed (Table , entries 1 and 2) . Alkylation of the CO group of ketones proved to be facilitated by a neighboring OH or other basic group at the α- or β-position; α-(dimethylamino)acetone is for example alkylated selectively in the presence of 3-pentanone (Table , entries 3–9). , A neighboring group effect was also identified for oxirane ring-opening, with heteroatom-containing α-substituents favoring the reaction (Table , entries 10 and 11) . Note that reaction of Bu 3 MnLi with oxiranes furnishes the corresponding alkenes, a reaction not observed with the alkyl Cu(I) reagents …”

Section: Reactions Of Maas Involving Nucleophile Ligand Transfer Proc...mentioning

confidence: 99%

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Mixed AggregAte (MAA): A Single Concept for All Dipolar Organometallic Aggregates. 2. Syntheses and Reactivities of Homo/HeteroMAAs

2013

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6. Conclusion 7706 Author Information 7706 Biographies 7707 Acknowledgment 7707 Abbreviations Used 7707 References 7708the corresponding allyl-and propargylchromium reagents that further react with a variety of electrophiles to afford the corresponding adducts in high yields. 102 Bu 6 CrLi 3 similarly behaves as a formal two-electron reductant with ketones and esters bearing a leaving group at the α-position to produce enolates that are intercepted with a variety of electrophiles with high selectivities (Table 8). 103 Such enolates are also capable of reacting with oxiranes to afford γand β-hydroxy esters, depending on the Lewis acid used as promoter. 2143.2.2. Two-Electron Transfers from M,Mn-HeteroMAAs (M = Li, MgX). In 1976, Cahiez et al. disclosed the possible reduction in THF of alkenyl bromides or iodides, as well as aryl chlorides or bromides, using i-PrMgCl in the presence of a catalytic amount of MnCl 2 . 215 The authors proposed the in situ formation of unstable i-Pr 3 MnMgCl and its decomposition by β-elimination to H 3 MnMgCl; reaction of the latter with the halide would then afford an unstable Mn(IV) intermediate, able Scheme 23 Scheme 24 Scheme 21 Scheme 22

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Section: Reactions Of Nu-homomaasmentioning

confidence: 98%

Section: Reactions Of Maas Involving Nucleophile Ligand Transfer Proc...mentioning

confidence: 99%

Mixed AggregAte (MAA): A Single Concept for All Dipolar Organometallic Aggregates. 2. Syntheses and Reactivities of Homo/HeteroMAAs

2013

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“…77,157Ð159 Chelate control of α-alkoxy substituents was not observed 158 despite the cheleselectivity reported for chemoselection of chromium(III) organyls. 48,160 Scheme 14 Influence of an α-stereocenter in the aldehyde reactant on the C4,C5-diastereoselection of the 3,4-anti-products…”

Section: Scheme 13 Recent Examples Of Syn-selective Hiyamaðnozaki Reamentioning

confidence: 99%

“…23,29 The advantage of the alkylchromium reagents is their excellent chemo-and cheleselectivity, 37,48 and their insensitivity to traces of water. 48,160,178,179 Lately only allylchromium reagents have been prepared by this method (see Section 3.2.1). 165 Apart from the extra step, the method is limited to intermolecular reactions, and mainly methylchromium(III) reagents have been used.…”

Section: Scheme 18mentioning

confidence: 99%

Recent Advances in Chromium(II)- and Chromium(III)-Mediated Organic Synthesis

Wessjohann¹,

Scheid²

1999

Synthesis

215

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Synthetic transformations utilizing chromium(II) or chromium(III) reagents, mainly CÐC-coupling reactions, are discussed. Chromium reagents find increasing application in complex total syntheses where other organometallics are difficult to apply. They are easy to prepare and exhibit extraordinary chemoselectivity and high diastereoselectivity. In this article emphasis is laid on recent results in synthetic procedures, on little known general aspects of (organo)chromium chemistry, and on areas not reviewed before. The most important recent advances include reactions catalytic in chromium ions, anti -selective Reformatsky-type aldol reactions with excellent asymmetric induction, domino radical/carbanion reactions, asymmetric chromium(III) catalyzed epoxide openings and homogeneous alkene polymerization catalysts. Some progress is also made in ligand controlled enantioselective reactions with Cr(II) reagents, but satisfying solutions remain a major challenge in the field.

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Addition of Organochromium Reagents to Carbonyl Compounds

Takai

2004

Organic Reactions

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Organochromium compounds can be prepared by two methods: (1) transmetallation from the corresponding organolithium, ‐magnesium, or –zinc compounds with chromium(III) halides, and (2) reduction of organic substrates, such as halides and unsaturated compounds with chromium(II) salts. The second method is usually the one ised because the first method suffers from low solubility of chromium(III) salts in ethereal solvents and from the difficulty of preparing organolithium compounds. Low‐valent chromium species are reducing agents. Reduction of various types of organic halides and compounds having unsaturated hetero‐hetero bonds with the chromium (II) species is discussed. Also described are the transmetallation to organochromium compounds from other organometallics, the nature of the carbon‐chromium bonds, and the X‐ray structure of chromium compounds. Reactions of organochromium reagents with carbonyl compounds and their scope and limitations are described. Included in this discussion are the geminal chromium reagents. Other reagents discussed are the chromium‐nickel compounds and alkylchromium and other organochromium reagents.

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E-don-gruppierungen organishcer verbindungen als bevorzugte angriffs= stellen für nucleophile, alkylierende übergangsmetallreagenzien; eine erste übersicht

Cited by 19 publications

References 4 publications

Mixed AggregAte (MAA): A Single Concept for All Dipolar Organometallic Aggregates. 2. Syntheses and Reactivities of Homo/HeteroMAAs

Mixed AggregAte (MAA): A Single Concept for All Dipolar Organometallic Aggregates. 2. Syntheses and Reactivities of Homo/HeteroMAAs

Recent Advances in Chromium(II)- and Chromium(III)-Mediated Organic Synthesis

Addition of Organochromium Reagents to Carbonyl Compounds

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