Lecture17outline

Lecture17outline - I Review Cross metathesis reactions can...

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I. Review • Cross metathesis reactions can be used to couple fragments if the products are more stable than the starting materials, as seen in the coupling of alkenes with α , β -unsaturated carbonyl compounds • Another trick for conducting cross metathesis reactions employs vigorous reflux conditions to remove ethylene from the system • Exposing ketones and aldehydes to acid in D 2 O results in deuterium incorporation at all α -positions (adjacent to the carbonyl) • This process proceeds through thermodynamically disfavored enol formation followed by protonation (deuteration) at the α -position • Enols are weak nucleophiles and weak bases • Exposing ketones and aldehydes to base in D 2 O results in deuterium incorporation at all α -positions • This reaction proceeds through enolate formation followed by protonation at the α - position • Enolates are more nucleophilic and basic than enols due to their negative charge • Enols and enolates are planar, so stereocenters adjacent to ketones and aldehydes are
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Lecture17outline - I Review Cross metathesis reactions can...

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