Remarkable Effect of Ethylene Gas in the Intramolecular Enyne Metathesis of Terminal Alkynes

Mori, Miwako; Sakakibara, Norikazu; Kinoshita, Atsushi

doi:10.1021/jo980896e

Cited by 293 publications

(209 citation statements)

References 19 publications

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“…Derivatives 16 were also cleanly converted to the pyrrolines but could, as we have described before, not be oxidized to the pyrroles because of the electron-withdrawing substituent on nitrogen (Table 2). [29] Looking at the reaction mechanism, two pathways are possible (Scheme 5 [13] reported that when working under "Moris conditions" [30] ethylene gas reacts with carbenoids of type 29 in a second catalytic cycle producing the metathesis products and thus explaining the dramatic effect of ethylene on both the yield and the reaction rate of Rucatalyzed enyne RCM reactions. As our experiments were performed under an inert nitrogen atmosphere, the fact that complete conversion is observed within 30 minutes tends to rule out the possibility of the ene-then-yne pathway, as this would contradict the low yields of enyne metathesis that predate Moris observations.…”

Section: Resultsmentioning

confidence: 99%

Enyne Metathesis–Oxidation Sequence for the Synthesis of 2‐Phosphono Pyrroles: Proof of the “Yne‐then‐Ene” Pathway

Dieltiens

Moonen

Stevens

2006

Chemistry A European J

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A new tandem reaction sequence has been developed for the synthesis of 2‐phosphono pyrroles. The sequence consists of ring‐closing enyne metathesis of a substituted aminophosphonate, containing a terminal alkyne and an internal alkene, in combination with in situ oxidation of the produced 3‐pyrrolines using tetrachloroquinone. By analyzing the formation of the end and certain byproducts, taking into account the difference in reactivity of different substrates and carefully studying spectroscopic data, it was found that the reaction proceeds by means of the “yne‐then‐ene” pathway. During the initiation phase, a new ruthenium carbene is formed which continues the propagation cycle.

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Section: Resultsmentioning

confidence: 99%

Enyne Metathesis–Oxidation Sequence for the Synthesis of 2‐Phosphono Pyrroles: Proof of the “Yne‐then‐Ene” Pathway

Dieltiens

Moonen

Stevens

2006

Chemistry A European J

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“…Subsequently, Mori's group went on to find that ethylene could be used to promote ring-closing enyne metathesis (eq 14). [24] This became known as "Mori's conditions." The reasons for the 'ethylene effect' were mechanistically unclear, but the procedure became widely used in the synthetic literature.…”

Section: Enyne Metathesismentioning

confidence: 99%

Ruthenium vinyl carbene intermediates in enyne metathesis

Diver

2007

Coordination Chemistry Reviews

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This review provides an overview of ruthenium vinyl carbene reactivity as it relates to enyne metathesis. Methods for the synthesis of metathesis-active and metathesis-inactive complexes are also summarized. Some of the early hypotheses about vinyl carbene intermediates in enyne metatheses were tested in the arena of synthetic chemistry and subsequently led to mechanistic studies. In these two areas, studies from the author's labs are described. There are still many unresolved questions in enyne metathesis that trace back to vinyl carbene reactivity. Hopefully this review will stimulate further investigation into vinyl carbene reactivity which should further refine our understanding of catalytic enyne metathesis.

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“…Furthermore, under an ethylene atmosphere (32,33), intermolecular ene-yne metatheses have been shown to proceed by ethylene-yne cross metathesis followed by a terminal diene-olefin cross metathesis (28). We believe that our system behaves similarly: ethylene-yne cross metathesis occurs first, affording a terminal 1,3-diene, followed by terminal diene-olefin metathesis macrocyclization.…”

Section: Resultsmentioning

confidence: 77%

Synthesis of (-)-longithorone A: Using organic synthesis to probe a proposed biosynthesis

Morales

Layton

Shair

2004

Proc. Natl. Acad. Sci. U.S.A.

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We present a full report of our enantioselective synthesis of (؊)-longithorone A (1). The synthesis was designed to test the feasibility of the biosynthetic proposal for 1 put forward by Schmitz involving intermolecular and transannular Diels-Alder reactions of two [12]-paracyclophane quinones. We have found that if the biosynthesis does involve these two Diels-Alder reactions, the intermolecular Diels-Alder reaction likely occurs before the transannular cycloaddition. The intermolecular Diels-Alder precursors, [12]-paracyclophanes 38, 49, 59, and 60, were prepared atropselectively, providing examples of ene-yne metathesis macrocyclization. The 1,3-disubstituted dienes produced from the macrocyclizations represent a previously unreported substitution pattern for intramolecular ene-yne metathesis. Protected benzylic hydroxyl stereocenters were used as removable atropisomer control elements and were installed by using a highly enantioselective vinylzinc addition to electron-rich benzaldehydes 26 and 27.A n intriguing question in natural product biosynthesis is whether nature uses Diels-Alder reactions. The answer to this question appears to be yes, because there are many examples of spontaneous Diels-Alder reactions in biosyntheses (1) as well as recently documented examples (2-4) of enzymatically influenced Diels-Alder reactions. Longithorone A (1) is a marine natural product that attracted our attention because of its unusual structure, but even more so because of the biosynthetic proposal of Schmitz and co-workers (5, 6) that invoked two Diels-Alder reactions. Schmitz has proposed that 1 arises from the combination of [12]-paracyclophane quinones 2 and 3 by an intermolecular Diels-Alder reaction, affording ring E, and a transannular (7) Diels-Alder reaction, generating rings A, C, and D (Fig. 1).We viewed this interesting proposal as an opportunity to use organic synthesis to make protected versions of 2 and 3 and test, in the laboratory, the feasibility of the proposed Diels-Alder reactions (8). In particular, we were hopeful that our experiments might suggest whether the intermolecular Diels-Alder reaction occurs preferentially between compound 4, which has already undergone a transannular Diels-Alder, and paracyclophane 2 to generate 1 or between paracyclophanes 3 and 2 to generate 5, followed by a transannular Diels-Alder to afford 1.The isolation (5) of longithorones B (9) and C, [12]-paracyclophane quinones that closely resemble the structures of 2 and 3, provided some support for the proposed biosynthesis of longithorone A (Fig. 2).We found it intriguing that longithorones B and C exhibit atropisomerism (10-12) and are single enantiomers. From these observations, we recognized that 2 and 3 must be constructed atropselectively to test whether the absolute and relative stereochemistry of 1 is derived solely from the planar chirality of 2 and 3. Finally, the isolation of longithorone I suggested that the biosynthesis of 1 may first involve an intermolecular Diels-Alder reaction between 2 and 3 followed by a...

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Remarkable Effect of Ethylene Gas in the Intramolecular Enyne Metathesis of Terminal Alkynes

Cited by 293 publications

References 19 publications

Enyne Metathesis–Oxidation Sequence for the Synthesis of 2‐Phosphono Pyrroles: Proof of the “Yne‐then‐Ene” Pathway

Enyne Metathesis–Oxidation Sequence for the Synthesis of 2‐Phosphono Pyrroles: Proof of the “Yne‐then‐Ene” Pathway

Ruthenium vinyl carbene intermediates in enyne metathesis

Synthesis of (-)-longithorone A: Using organic synthesis to probe a proposed biosynthesis

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