New Polyfunctional Magnesium Reagents for Organic Synthesis

Rottländer, Mario; Boymond, Laure; Bérillon, Laurent; Leprêtre, Anne; Varchi, Greta; Avolio, Salvatore; Laaziri, Hamid; Quéguiner, G.; Ricci, Alfredo; Cahiez, Gérard; Knöchel, Paul

doi:10.1002/(sici)1521-3765(20000303)6:5<767::aid-chem767>3.0.co;2-x

Cited by 104 publications

(43 citation statements)

References 12 publications

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“…[36] The use of highly active magnesium, such as ªRieke-magnesiumº, [37] is not possible since the presence of electron-poor functional groups such as a carboxy or cyano group inhibits the formation of the Grignard reagent. [39] The mild conditions required for the bromine ± magnesium exchange were first discovered by Villie Â ras who demonstrated that highly reactive magnesium carbenoids such as 35 can be prepared at À 78 8C. [39] The mild conditions required for the bromine ± magnesium exchange were first discovered by Villie Â ras who demonstrated that highly reactive magnesium carbenoids such as 35 can be prepared at À 78 8C.…”

Section: Polyfunctional Organomagnesium Reagentsmentioning

confidence: 99%

New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis

Boudier

Bromm

Lotz

et al. 2000

Angew. Chem. Int. Ed.

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315

115

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In the second half of the twentieth century much effort was invested in the preparation of highly reactive polar organometallic reagents. The high reactivity of these reagents precluded the presence of many functional groups and often good chemoselectivities and stereoselectivities could only by achieved by transmetalation reactions. The synthesis of increasingly complex target molecules and the desire to avoid tedious protection–deprotection steps has led inevitably to the use of functionalized organometallic reagents in retrosynthesis. In the last fifteen years, the generation of organic derivatives of numerous metals and metalloids (Li, Mg, B, Zn, Sn) was investigated. In this review the most important preparations and applications of organometallic reagents in organic synthesis will be covered, with particular emphasis on organozinc reagents.

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Section: Polyfunctional Organomagnesium Reagentsmentioning

confidence: 99%

New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis

Boudier

Bromm

Lotz

et al. 2000

Angew. Chem. Int. Ed.

Self Cite

315

115

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“…This was indeed the case as demonstrated by the isomerization of (Z)-1-triphenylgermyl-1-dodecene into the (E)-isomer. Heating a benzene solution of (Z)-1-triphenylgermyl-1-dodecene at 60 C in the presence of catalytic amounts of Ph 3 GeH and Et 3 B gave (E)-isomer exclusively. The isomerization is explained by addition-elimination sequences of the triphenylgermyl radical (Scheme 14).…”

Section: Et 3 B-induced Radical Addition Of R 3 Snh and R 3 Geh To Acmentioning

confidence: 99%

“…Knochel et al have reported the halogen-magnesium exchange for the preparation of polyfunctional organomagnesium reagents. 60,61 Aryl, heteroaryl, and alkenyl halides bearing electron-withdrawing groups or metal-directing groups can be converted into the corresponding magnesium reagents by treating with i-PrMgBr or i-Pr 2 Mg in THF at low temperatures. However, substrates are often limited to rather electron-poor aryl or alkenyl halides, particularly in the case of bromides.…”

Section: 59mentioning

confidence: 99%

Highly Selective Synthetic Reactions by the Combined Use of Organometallic Reagents and Radical Species

Oshima¹

2008

Bulletin of the Chemical Society of Japan

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During these thirty years, we have pursued new methodologies in organic synthesis and developed many synthetically useful reactions. Among them, four topics are described in this article. (1) Regio-and stereoselective silylmetalation of acetylenes has been examined. Whereas platinum-or copper-catalyzed silylmagnesation of terminal acetylenes afforded (E)-1-silyl-1-alkene exclusively, palladium-catalyzed silylalumination with PhMe 2 Si-AlEt 2 provided 2-silyl-1-alkenes with high regioselectivity. (2) Triethylborane induced radical addition of Ph 3 SnH to acetylenes gave 1-triphenylstannyl-1-alkenes in the presence of small amount of oxygen. The reaction has two distinguishing characteristics. One feature is that Et 3 B can initiate the radical reaction at low temperature, such as À78 C. (3) The other distinctive feature of Et 3 B-induced radical reaction is that many solvents could be used for the reaction. Thus, water was chosen as a solvent, and Et 3 B-induced atom-transfer radical cyclization of iodo acetals and iodoacetates in water was examined. (4) Three types of organometallic ate complexes, R 3 MnMgBr, R 3 MgLi, and R 3 Co(L 2 )MgBr, were prepared and used for organic synthesis. Treatment of gem-dibromocyclopropane with trialkylmanganate provided alkylated cyclopropane after aqueous workup. Aryl and alkenyl halides could be converted into the corresponding magnesium reagents by the action of trialkylmagnesate via halogen-magnesium exchange. Finally, synthetic reactions catalyzed by cobalt complexes are described. Without suffering from -elimination, cobalt complexes allow cross-coupling reactions of alkyl halides with Grignard reagents. Silylmetalation of Acetylenes and Its Application to the Stereoselective Synthesis of Steroidal Side ChainsIn 1982, we started an investigation on the stereoselective synthesis of the side chain of a plant growth steroidal hormone, brassinolide. Our synthesis route, which consists of three key reactions, is shown in Scheme 1.We began by studying the last step (c), selective ring opening of ,-epoxy alcohol. Among many organometallic compounds examined, organoaluminum reagents were found to be effective for the regio-and stereoselective ring opening of epoxy alcohol to give 1,2-diols. 1 The reaction proceeds with inversion at the reacting center. In the next step (b), we had to develop a new method of preparing threo epoxy alcohol 3 form (E)-allylic alcohol 2a. The vanadium-catalyzed epoxidation of (E)-allylic alcohol gave the erythro isomer as a main product. On the other hand, m-CPBA epoxidation gave the threo isomer as a major product, but the selectivities of these reactions were rather low and not enough for our purpose. This problem was solved by substitution of an appropriate hydrogen on the double bond by a bulky Me 3 Si group.2 Treatment of 2b with VO(acac) 2 -t-BuOOH or m-CPBA gave threo epoxy alcohol 3 with high stereoselectivity (99%). The Me 3 Si group was easily removed by treatment with n-Bu 4 NF or CsF in DMSO, and the desilylation of epoxysilane proceeded wi...

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“…Unfortunately, the presence of such important electron-withdrawing functional groups as esters or cyano functions inhibits the formation of Grignard reagents [18]. Complementarily, halogen-magnesium exchange [19] has proven to be an excellent method for preparation of functionalized organomagnesium compounds. Thus, treatment of 4-iodobenzonitrile 13 with iPrMgBr or iPr 2 Mg in THF at À25 C furnishes the corresponding organomagnesium reagent, which is transmetalated to produce the desired functionalized organocopper 14.…”

Section: Transmetalation Reactions Producing Organocopper Reagentsmentioning

confidence: 99%

“…After cleavage from the resin, a range of functionalized products may be obtained. Use of the resin-bound bromothiophene 41 as starting material furnishes the copper reagent 42, which produces the carboxylic acid 43 after allylation and cleavage from the resin (Scheme 2.10) [19,24]. …”

Section: Transmetalation Reactions Producing Organocopper Reagentsmentioning

confidence: 99%

Transmetalation Reactions Producing Organocopper Reagents

Knöchel

Betzemeier

2002

Modern Organocopper Chemistry

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New Polyfunctional Magnesium Reagents for Organic Synthesis

Cited by 104 publications

References 12 publications

New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis

New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis

Highly Selective Synthetic Reactions by the Combined Use of Organometallic Reagents and Radical Species

Transmetalation Reactions Producing Organocopper Reagents

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