Medium Size Ether Ring Formation of C-Alkynylated Sugars<i>via</i>Dicobalthexacarbonyl Complexes

Isobe, Mitsuaki; Yenjai, Chavi; Tanaka, Shigeyoshi

doi:10.1055/s-1994-23047

Cited by 52 publications

(20 citation statements)

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“…55 (Scheme 11), would preclude a spontaneous ring-forming reaction, Isobe et al, introduced an alternative ring-recyclization strategy to medium size 7, 8, 9 and 10-membered rings by positioning the nucleophilic hydroxyl group at the, otherwise, terminal site of the acetylene (Scheme 11). [25] In order to induce the Nicholas cyclization, the precursors 54 were prepared by C-glycosidation of tri-O-acetyl-D-glucal 6, with trimethylsilylacetylene followed by palladium catalyzed ene-yne coupling reaction with the appropriate vinyl iodide, 53 (Scheme 11). Then, cobalt complexation and acid treatment of the C-dicobalt hexacarbonyl allylic glycosides 54, generated the intermediate Nicholas cations 55, by a process in which an initially formed (C-1) cis allylic cation, isomerized to the more stable trans allylic cation.…”

Section: Dicobalt Hexacarbonyl Mediated Formation Of Ether Rings Frommentioning

confidence: 99%

Alkyne dicobalt complexes in carbohydrates: Synthetic applications

Gómez

López

2020

Recent Trends in Carbohydrate Chemistry

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The complexation of alkynes to form dicobalt hexacarbonyl derivatives facilitates the formation, under acid catalysis, of highly stabilized propargylic cations whose reaction with nucleophiles to form propargylic compounds, currently known as the Nicholas reaction, has found ample use in organic synthesis. This transformation has shown to be particularly useful when applied to carbohydrate derivatives. In this chapter, we provide a brief overview on this subject pioneered by early contributions from Isobe's research group. Thus, carbohydrate-derived dicobalt hexacarbonyl complexes have been used in the epimerization of C-alkynyl glycosides, pyranose ring-opening nucleophile trapping reactions, pyranose ring-opening ring-recyclization leading to medium-sized oxacycles, glycosylation strategies, C-glycosylation and pyranose to carbocycle transformations among others. Finally, contributions from our research group focusing on the synthetic applications of Ferrier-Nicholas cations are also presented.

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Section: Dicobalt Hexacarbonyl Mediated Formation Of Ether Rings Frommentioning

confidence: 99%

Alkyne dicobalt complexes in carbohydrates: Synthetic applications

Gómez

López

2020

Recent Trends in Carbohydrate Chemistry

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“…Finally, sodium hypophosphite [37] and high pressure H 2 / Rh (Rh/C or Wilkinson's catalyst), [38] may be considered as potentially useful reagents for reductive decomplexation. While these have not been reported as effecting this transformation on (cycloheptyne)dicobalt complexes, they have been used on the corresponding cyclic ethers, and therefore have a high probability for successful use in the all-carbon ring systems.…”

Section: Reductive Removalmentioning

confidence: 99%

(Cycloheptyne)dicobalt Complexes in Organic Synthesis

Green

2008

Eur J Org Chem

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Cobalt complexes of cycloheptynes are thermally stable compounds, unlike their metal‐free counterparts. The past decade has seen the development of a number of reliable methods for their preparation, and a substantial delineation of the reactions they undergo and tolerate. In turn, these developments have resulted in the exploitation of cycloheptynedicobalt complexes in synthesis. This review details the recent developments in the chemistry of these compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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“…In several instances, variants of the Nicholas reaction have shown the ability to form cycloheptyne and cyclooctyne complexes readily. The synthetic utility of these cycloalkyne complexes has also been aided by the recent development of methods of removal of the cobalt unit in tandem with carboxylation [43], reduction [44,45], or hydrosilylation [43c] of the triple bond.…”

Section: Cyclization Reactions -Exocyclic Alkynes Scheme 2 Electrophmentioning

confidence: 99%

“…To date this is still the only successful report of a cyclohexyne-Co 2 (CO) 6 complex. More recently, Tanino and Kuwajima have reported that a trans-decalin system bearing an exocyclic alkylidene and a propargyl acetate -Co 2 (CO) 6 complex undergoes cyclization, followed by one of two processes [44]. Highly Lewis acidic organoaluminum reagents give cyclization followed by a proton loss to form a 7,6,6-system (20a).…”

Section: Cyclization Reactions -Exocyclic Alkynes Scheme 2 Electrophmentioning

confidence: 99%

“…MOM ethers perform similarly, but less cleanly. Finally, Mukai and Hanoaka have extended their cyclic ether forming reactions to 8-membered cases by employing a trimethylsilylmethyl substituted tetrahydrofuran (44), which uses a propargyl cation that induces ring opening a C-O bond of an oxolane to form a β-silyl cation; the latter then loses H + or "Me 3 Si + " [80]. Rather than employing a Lewis acid for propargyl cation formation however, conversion of the propargyl alcohol function to the mesylate was the only protocol found to be efficient in inducing this process.…”

Section: Migrationsmentioning

confidence: 99%

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Chemistry of Propargyldicobalt Cations Recent Developments in the Nicholas and Related Reactions

Green

2001

COC

146

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Abstract:The chemistry of propargyldicobalt cations, also known as the Nicholas reaction, is reviewed, with a focus on the developments since 1995. Advances in the understanding of the fundamental properties, such as structure, stability, and reactivity, of both the hexacarbonyl complexes and those bearing other ligands are discussed. All reactions involving propargyl cation dicobalt complexes are covered, including those stemming from ionization of propargylic leaving groups and those created by electrophilic addition to enyne complexes. Migration reactions involving either initiation or termination by propargyl cation complexes are included, as are the generation and reactions of propargyldicobalt radicals. Cyclization reactions employing these cations have received much attention, in cases with the alkynedicobalt unit located in both exocyclic and endocyclic positions, and these reports are described. Particular attention is paid to preparation of medium ring cycloalkyne complexes and their heterocyclic analogues. In addition, there is discussion of the progress in the in selectivity of these reactions, especially in terms of introduction of asymmetry at the propargylic site. Finally, recent applications of Nicholas reaction chemistry in the synthesis of natural products and related compounds are reported.

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Medium Size Ether Ring Formation of C-Alkynylated SugarsviaDicobalthexacarbonyl Complexes

Cited by 52 publications

References 0 publications

Alkyne dicobalt complexes in carbohydrates: Synthetic applications

Alkyne dicobalt complexes in carbohydrates: Synthetic applications

(Cycloheptyne)dicobalt Complexes in Organic Synthesis

Chemistry of Propargyldicobalt Cations Recent Developments in the Nicholas and Related Reactions

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