Lecture16outline

Lecture16outline - I. Review Most additions of carbon or...

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I. Review • Most additions of carbon or hydrogen nucleophiles into carbonyl groups are irreversible because the product are much more stable than the starting materials • Sufficiently stabilied carbon nucleophiles should add to carbonyl groups reversibly • Cyanide is a stable carbon nucleophile because the lone pair is in an sp orbital and the nitrogen inductively stabilizes the negative charge • Cyanide adds to ketones and aldehydes in the presence of mild acids like NH 4 Cl to form cyanohydrins • Cyanohydrins are stable toward acid but are unstable in base, allowing them to serve as cyanide sources that can be handled with fewer toxicity concerns • Cyanohydrin formation in the presence of silyl chlorides provides cyanohydrin silyl ethers, which can be deprotonated to react with electrophiles • The products of these reactions can be converted to ketones by cleaving the silyl ether with fluoride, providing another example of "acyl anion" chemistry • The regiochemistry of elimination reactions is difficult to control and smarter
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Lecture16outline - I. Review Most additions of carbon or...

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