First Direct Synthesis of Optically Active 3‐Methylcyclopentene

Silwka, Hans‐Richard; Hansen, Hans‐Jürǵen

doi:10.1002/hlca.19840670212

Cited by 17 publications

(5 citation statements)

References 56 publications

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“…iodide, [1][2][3][4][5][6]10,11] sulfonate [1][2][3][4][5][6]12] and sulfinate [1][2][3][4][5][6][13][14][15][16][17] esters have all been used successfully in Ramberg-Bäcklund-type reactions, not a great deal of research into the use of different leaving groups in this process has been reported.…”

Section: Introductionmentioning

confidence: 99%

The Epoxy‐Ramberg–Bäcklund Reaction (ERBR): A Sulfone‐Based Method for the Synthesis of Allylic Alcohols

2006

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Section: Introductionmentioning

confidence: 99%

The Epoxy‐Ramberg–Bäcklund Reaction (ERBR): A Sulfone‐Based Method for the Synthesis of Allylic Alcohols

2006

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“…This assumption is supported by comparing the [ab20 value of -155.8°(c = 0.012, benzene) [or -163.4°when corrected for the optical purity of (+)-2] obtained for (3S)-1 with the [ab20 value of +157.5°(c = 0.012, benzene) previously reported for enantiopure (3i?)-l. 8 In contrast, by employing concentrated solutions of 2 (~50% wt), an isomeric mixture of all three methylcyclopentenes is produced, presumably due to the formation, under these particular conditions, of reduced molybdenum species which can potentially serve as catalysts for the isomerization process. 15 Apparently, this is the first time that isomerization accompanying a DMC catalyzed by 3 has been observed.…”

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confidence: 99%

Main-Chain Chiral Polymers from .beta.-Citronellene via Tandem Diene Metathesis Cyclization/Ring-Opening Metathesis Polymerization

Sita¹

1995

Macromolecules

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The synthesis of non-naturally occurring optically active polymers that possess main-chain chirality remains a topic of current interest.' In this regard, the polymerization of enantiomerically-enriched chiral monomers in which stereogenic centers of the monomer become those of the polymer backbone guarantees that complete control of the absolute and relative configurations of centers within the main chain, and hence, the "handedness" and tacticity, respectively, of the new material, can be a~h i e v e d .~,~ Accordingly, through this strategy, the potential exists to produce not only new materials with maximum optical rotatory power but also those with well-defined backbone conformations, especially in cases where torsional interactions between backbone substituents limits the conformational space that can be probed by the polymer chain.4 Related to this, we have been interested in further delineating the factors which control the polymerizability of cyclic olefins via olefin metathesis, and in particular, of exoand endo-substituted cyclopentenes where we have previously shown that the relief of torsional strain can drive the polymerization process irreversibly f~r w a r d .~ Thus, as a natural extension of these studies, we were intrigued with the idea of generating new classes of optically active polymers and copolymers from readily available, torsionally-strained, chiral cyclic monomers through "living" ring-opening metathesis polymerization (ROMP).6 Herein, we now report the first results regarding the realization of this goal which include (1) the large scale syntheses of isomerically pure (3R)-and (3S)-3-methylcyclopentene (3-MCP) (1) via diene metathesis cyclization (DMQ7 of (-)-and (+)-b-citronellene (2), respectively, and (2) the first unequivocal demonstration of the ROMP of (3R)-and (3S)-3-MCP to yield polymers and copolymers with high optical rotatory power.3-Methylcyclopentene (1) is notoriously difficult to obtain in isomerically and optically pure form, and previously, this has only been accomplished by a lengthy multistep stereoselective synthesis which provided less than 100 mg of the final producte8 Given this, we envisioned the production of large amounts of (3R)-and (3s)-1 via the DMC of commercially available (-1-and (+)-/3-citronellene according t o Scheme 1. As this scheme indicates, the DMC of 2 could indeed be accomplished in high yield by employing Schrock's molybdenum imido alkylidene complex, [(CF3)2CH3COI&lo-[CHC(Me)zPh][ N(2,6-iPr2C6H3)10 (3), which has previously been used for the DMC of a variety of other a,wd i e n e~.~J l J~ In the present example, however, several important features can be noted. First, on a small scale, using 2 mol % of 3, this cyclization reaction, which is 0.75 M in (+)-2 (of 95% optical purity),12J3 proceeds quantitatively in toluene at room temperature within 30 min to provide isomerically pure (3S)-1 as followed by 'H NMR spectroscopy. More importantly, the DMC of technical grade (-)-2 (85% optically pure)12 of 90% 0024-9297/95/2228-0656$09.00/0 Scheme 1 ...

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“…Found: C 53.47; H 10.72; N 10.63. ( R )-9a is a known compound in literature, but no spectral data were available. , …”

Section: Methodsmentioning

confidence: 99%

Asymmetric Synthesis of Chiral N-Sulfinyl 3-Alkyl- and 3-Arylpiperidines by α-Alkylation of N-Sulfinyl Imidates with 1-Chloro-3-iodopropane

2010

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α-Alkylation of N-sulfinyl imidates with 1-chloro-3-iodopropane successfully led to 2-substituted N-tert-butanesulfinyl-5-chloropentanimidates in acceptable diastereomeric ratios (dr 67/33 to 72/28) and good yields (74-86%). Subsequent reduction with NaBH(4) led to the corresponding 2-substituted N-tert-butanesulfinyl-5-chloropentylamines, which could be cyclized to a range of new chiral 3-substituted N-tert-butanesulfinylpiperidines using NaH in DMSO. Finally, the N-tert-butanesulfinylpiperidines could be efficiently deprotected to enantiomerically pure 3-alkyl- and 3-arylpiperidine hydrochlorides.

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First Direct Synthesis of Optically Active 3‐Methylcyclopentene

Cited by 17 publications

References 56 publications

The Epoxy‐Ramberg–Bäcklund Reaction (ERBR): A Sulfone‐Based Method for the Synthesis of Allylic Alcohols

The Epoxy‐Ramberg–Bäcklund Reaction (ERBR): A Sulfone‐Based Method for the Synthesis of Allylic Alcohols

Main-Chain Chiral Polymers from .beta.-Citronellene via Tandem Diene Metathesis Cyclization/Ring-Opening Metathesis Polymerization

Asymmetric Synthesis of Chiral N-Sulfinyl 3-Alkyl- and 3-Arylpiperidines by α-Alkylation of N-Sulfinyl Imidates with 1-Chloro-3-iodopropane

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