New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis

Boudier, Andreas; Bromm, Lars O.; Lotz, Matthias; Knöchel, Paul

doi:10.1002/1521-3773(20001215)39:24<4414::aid-anie4414>3.3.co;2-3

Cited by 31 publications

(34 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…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

View full text Add to dashboard Cite

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...

show abstract

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

View full text Add to dashboard Cite

show abstract

“…Concerning the second point, we have been interested in the last several years in the study of functionalized organometallic compounds because in their reaction with electrophiles they are able to yield polyfunctionalized molecules in only one reaction step [3]. Among the different possibilities, we have studied mainly functionalized organolithium intermediates due to their high reactivity, even at low temperatures, based on the high polarity of the carbon-lithium bond [4].…”

Section: Introductionmentioning

confidence: 99%

Ring Opening of Heterocycles by an Arene‐Catalyzed Lithiation

Yus

2004

ChemInform

View full text Add to dashboard Cite

Abstract:The ring opening of different three-, four-, five-and six-membered oxygen-, nitrogen-and sulfur-containing saturated heterocycles using lithium and a catalytic amount of an arene (naphthalene or DTBB) yields a series of functionalized organolithium compounds, which, by reaction with different electrophiles, allow the preparation of polyfunctionalized molecules in only one synthetic operation.

show abstract

“…[1][2][3] Organolithium compounds constitute a unique class of reagents due to their characteristic reactivity, the functionalized organolithiums and the polylithium synthons being of special interest in organic synthesis. [4][5][6][7][8][9][10][11][12][13][14][15] Deprotonation and halogen/lithium exchange, employing commercially available organolithium reagents, are conventionally the main routes for the preparation of other organolithium reagents.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective catalytic lithiation using a chiral binaphthyl derivative as electron carrier

Flores¹,

Pastor²,

Yus³

2013

Arkivoc

View full text Add to dashboard Cite

Dedicated to Prof. Rosa M.ª Claramunt on the occasion of her 65th birthday AbstractThe lithiation, of the secondary chloride 2, catalyzed by binaphthyl derivatives, i.e. BINAM 4, BINOL 5, BINAP 6, H8-BINAP 7, Tol-BINAP 8, 2,2'-bis(pyrrolidin-1-yl)-1,1'-binaphthalene 9, and 2,2'-dimethyl-1,1'-binaphthalene 11, in the presence of different ketones has been studied, yielding the corresponding alcohol derivatives 3 and 12-16 in moderate to good yields. Binaphthyl derivative 11 has revealed to be very active as catalyst in the lithiation process at room temperature, and has allowed the preparation of the alcohol derivatives with enantioselectivities up to 50%.

show abstract

New Applications of Polyfunctional Organometallic Compounds in Organic Synthesis

Cited by 31 publications

References 0 publications

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

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

Ring Opening of Heterocycles by an Arene‐Catalyzed Lithiation

Enantioselective catalytic lithiation using a chiral binaphthyl derivative as electron carrier

Contact Info

Product

Resources

About