Single and double ring closing metathesis in the formation of dihydropyrans and bisoxacyclic systems with a quaternary centre

Schmidt, Bernd; Wildemann, Holger

doi:10.1039/b004302h

Cited by 37 publications

(29 citation statements)

References 49 publications

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“…During the investigation of double RCM as a tool for rapid assembly of bisoxacyclic frameworks we investigated the behaviour of allyl ethers 113. Here, ring closure proceeds with high selectivity to the "dumbbell"-type product 114, whereas the fused product 115 could not even be detected in trace amounts (Scheme 35) [96]. The same result had previously been obtained by Mioskowski et al for a number of tetraenes.…”

supporting

confidence: 68%

"Ring Closing Metathesis of Substrates Containing more than two C-Cdouble Bonds: Rapid Access to Functionalized Heterocycles"

Schmidt¹,

Hermanns

2006

COC

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In most cases where ring closing metathesis is applied to the synthesis of heterocycles, α,ω-dienes are used as precursors. If substrates containing more than two double bonds are subjected to a metathesis reaction, carba-or heterocycles bearing additional exocyclic alkene functionality result, or multiple ring closing processes occur. This offers interesting and potentially very useful synthetic perspectives. On the other hand, selectivity problems need to be addressed as the cyclization of substrates with more than two double bonds available for olefin metathesis may result in constitutional isomers or stereoisomers. This review highlights problems and opportunities evolving from ring closing metathesis of tri-, tetra-, and polyenes as a strategy for the selective synthesis of functionalized heterocycles. The chapter on RCM of trienes is subdivided according to the symmetry of the metathesis precursor. The following two chapters deal with the double or multiple RCM of tetra-or polyenes. These processes are further classified according to the preferred cyclization mode. Finally, the application of cascade or domino metathesis reactions to the synthesis of heterocycles will be discussed. These processes can be classified into those where exclusively C-C-double bonds take part in the metathesis reaction, and those where one or more C-C-triple bonds are involved.

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supporting

confidence: 68%

"Ring Closing Metathesis of Substrates Containing more than two C-Cdouble Bonds: Rapid Access to Functionalized Heterocycles"

Schmidt¹,

Hermanns

2006

COC

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“…Ring closing metathesis reactions : Irrespective of the actual structure of the complex derived from [RuCl 2 (PPh 3 ) 3 ] and propargyl alcohol 5 , the excellent catalytic activity of this material was very quickly recognized 8, 9, 13–17. When applied to bis(allyl)tosylamide 9 , the presence of only 1 mol % of 3 b is sufficient to form the cyclized product 10 in essentially quantitative yield after 2 h reaction time at ambient temperature.…”

Section: Resultsmentioning

confidence: 99%

Evidence for the Formation of Singly Bonded Dimers During the Reductive Electrochemistry of Methanofullerenes

Oçafrain¹,

Herranz²,

Marx³

et al. 2003

Chemistry A European J

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Four methanofullerene derivatives, with phosphonate or sulfone groups attached to a C(60) core through a Bingel procedure, were synthesized to probe their stability upon electrolytic reduction. Derivatives 1 and 2 are the most stable upon electroreduction and do not exhibit retro-cyclopropanation reactions until more than three electrons per C(60) derivative are transferred. The cyclopropane ring is then removed and C(60)(>CH(2))(n) (n=1-3) products result from reactions of the trianion of C(60) with the solvent, CH(2)Cl(2). The situation with diphosphonate 3 or phosphonatecarboxylate 4 is dramatically different. For 3, quantitative retro-cyclopropanation occurs when 2.8 e(-) per molecule are transferred. In the case of 4, when more than two electrons per molecule are transferred, there is evidence of the reversible formation of a very stable intermediate, which is oxidized at a potential 500 mV more positive than the first fullerene-based reduction of the parent compound. Electrolysis of a simple C(70)-Bingel monoadduct (5) also exhibits the formation of a similar intermediate. On the basis of cyclic voltammetry, ESR spectroscopy, and MALDI analysis of products, the intermediate observed during the electrolysis of compounds 4 and 5 is assigned to a dimeric structure.

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“…This aspect of olefin metathesis has recently been reviewed by us. [29] Particularly relevant for the subject of this study are reports where different modes of cyclization result in different ring sizes, [30] such as the RCM-based synthesis of fused vs. "dumbbell"-type bicyclic lactams, [31,32] the strong preference for "dumbbell"-type oxacycles in the RCM of tetra- [33,34] or hexaenes. [35] Parallel to our preliminary account on the control of ring size-selectivity in RCM reactions of trienes 2, [36] two reports by Crimmins et al were published where the regioselective ring closure of structurally closely related trienes is described and efficiently used in the total syntheses of the Annonaceous acetogenin (À)-mucocin [37] and the microbial metabolite (+)-SCH 351448.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Dihydrofurans and Dihydropyrans with Unsaturated Side Chains Based on Ring Size‐Selective Ring‐Closing Metathesis

Schmidt

Nave

2007

Adv Synth Catal

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Enantiomerically pure 1,5-hexadiene-3,4-diol, derived from d-mannitol in a few steps, may serve as a starting material for enantiopure dihydropyrans and dihydrofurans bearing an unsaturated side chain which is amenable for further synthetic transformations. The synthesis relies on a ring sizeselective ring-closing metathesis reaction of a triene. Most likely, a catalyst-directing effect of an allylic hydroxy group is responsible for the selectivity.

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Single and double ring closing metathesis in the formation of dihydropyrans and bisoxacyclic systems with a quaternary centre

Cited by 37 publications

References 49 publications

"Ring Closing Metathesis of Substrates Containing more than two C-Cdouble Bonds: Rapid Access to Functionalized Heterocycles"

"Ring Closing Metathesis of Substrates Containing more than two C-Cdouble Bonds: Rapid Access to Functionalized Heterocycles"

Evidence for the Formation of Singly Bonded Dimers During the Reductive Electrochemistry of Methanofullerenes

Synthesis of Dihydrofurans and Dihydropyrans with Unsaturated Side Chains Based on Ring Size‐Selective Ring‐Closing Metathesis

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