Relay Ring Closing Metathesis

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Relay Ring Closing Metathesis

• Variations on a Theme

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RRCM (Relay Ring Closing Metathesis)

• RCM
• Powerful and widely used method
• Limitations
• Sterically hindered alkenes
• Electronically deactivated alkenes

• RRCM
• Substrate designed to dictate the sequence of
  metathesis events through the individual steps of
  the RCM
• Substrate controlled reaction
• Intramolecular loading of Ru catalyst

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Increasing Reactivity By RRCM
ECO2Et
Hoye et al JACS 2004, 126, 10210
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Bidirectional RRCM

• Demonstrates cyclization
• Onto an electron deficient alkene 6 to 7
• Into an electron deficient alkene 8 to 7

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RRCM Choreography
with G2
with G1
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Non Obvious Advantage

• Remote atom and all it bears is expendable during
  RRCM.
• Hoye used larger groups near the alcohol to
  increase resolution.

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Retrosynthetic Analysis of Oximidine III
Porco Angew. Int. Ed. 2004,43, 3601
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Metathesis Strategy
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Enyne Synthesis
Hansen, E.P. Lee,D. Org. Lett. 2004, 6, 2035
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Cross Metathesis of Conjugated Enynes
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Cross Metathesis of Conjugated Enynes
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Mechanism of CM without Relay
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Cross Metathesis
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Cross Metathesis of Conjugated Enynes
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CM Metathesis with Relay