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Carbanions and Base-catalyzed Formation of Carbon-Carbon Bonds

Carbanions and Base-catalyzed Formation of Carbon-Carbon Bonds. Formation of carbon-carbon bond. 1. Free radical carbon. 2. Charged or polar carbon. shape of the carbanion. I. Formation and related principle of carbanion ( concepts and mechanisms) Review. conjugated with other

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Carbanions and Base-catalyzed Formation of Carbon-Carbon Bonds

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  1. Carbanions and Base-catalyzed Formation of Carbon-Carbon Bonds

  2. Formation of carbon-carbon bond 1. Free radical carbon 2. Charged or polar carbon

  3. shape of the carbanion • I. Formation and related principle of carbanion ( concepts and mechanisms) • Review conjugated with other double bond

  4. Formation of carbanion 1.exchanging of organometallic compound and H 2.exchanging of organometallic compound and halides 3.reduction of halides with metal 4.abstraction of activating H with base

  5. Activating group for the neighboring H • NO2 > COR > CN > CO2R • Strength order of some commonly used bases:

  6. Factors influencing the stability of carbanions • 1. Conjugation • 2. Induction • 3. Hybridization style • 4. Aromaticity • The reactions of carbanions • 1. With carbonyl-containing compounds • 2. With alkyl halides

  7. II. Condensations of Carbanions with Aldehydes and Ketones • a) The Aldol Condensation Mechanism

  8. Ketone Rate-determining step

  9. Some applications of aldol condensation One aldehyde containing no active hydrogen: Formaldehyde is the most reactive among the aldehydes

  10. b) The Claisen Reaction

  11. c) The Perkin Reaction

  12. Compounds for the similar purpose as azalactone

  13. d) The Stobbe Condensation

  14. e) The Darzens Reaction The net result:

  15. f) Other Condensations of Aldol Type

  16. g) The Knoevenagel Reaction Ketone do not undergo the reaction with malonic acid or its esters, but do so with cyanoacetic acid and its ester.( with more highly active a-hydrogen.

  17. III.Condensations of Carbanion with Esters • a) The Claisen Condensation

  18. Mixed Claisen Condensations

  19. b) The Dieckmann Condensation Intramolecular Claisen condensation Forming five- or six-membered ring

  20. c) The Thorpe Reaction For the syntheses of various cyclic compounds In a very dilute ether solution Using hindered and less nucleophilic base like LiNEtPh

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