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17.5 The Wittig and Related Reactions

Main Menu. 17.5 The Wittig and Related Reactions. The Wittig Reaction (formation of alkenes). General Reaction:. R´ and R” can be H or alkyl group. Phosphine oxide. Wittig reagent (a phosphonium ylide ). General Reaction:. base. Formation of Wittig Reagents. A phosphonium salt.

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17.5 The Wittig and Related Reactions

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  1. Main Menu 17.5 The Wittig and Related Reactions The Wittig Reaction (formation of alkenes) General Reaction: R´ and R” can be H or alkyl group. Phosphine oxide Wittig reagent (a phosphoniumylide)

  2. General Reaction: base Formation of Wittig Reagents A phosphonium salt Ph: phenyl • The alkyl halides need to have at least one H. Example: Potassium tert-butoxide

  3. Mechanism of Wittig Reaction oxaphosphetane betaine

  4. Examples of Wittig Reaction major minor Wittig reagents favor the Z (cis) isomer.

  5. Horner-Emmons reaction (general reaction): Reactions of Aldehydes and Ketones with Horner-Emmons Reagent R = Et (most common) Phosphate diester Horner-Emmons reagent

  6. Arbuzov (Perkow) reaction: Formation of Horner-Emmons Reagent base Stabilized carboanion R = alkyl, acyl or R’OC(O)-

  7. Mechanism of Horner-Emmons Reaction oxaphosphetane betaine Water insoluble Water soluble

  8. Examples of Horner-Emmons Reaction > 99% Horner-Emmons reagents favor the E (trans) isomer.

  9. 1. What could be the reagent for the following transformation? Learning Check 2. What should be the product from the following reaction?

  10. Main Menu 3. What could be the product for the following reaction? Learning Check

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