Chapter 19-3

Chapter 19-3 - 11 CHEM 262 Wei You Chapter 19 Enolate...

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Unformatted text preview: 11 CHEM 262 Wei You Chapter 19. Enolate Anions (3) 22 Enamines • Enamines are formed by the reaction of a 2° amine with the carbonyl group of an aldehyde or ketone – the 2° amines most commonly used to prepare enamines are pyrrolidine and morpholine Pyrrolidin e Morpholine N O N H H 33 Mechanism of Imine Formation 44 Mechanism of Enamine Formation 55 Examples + H + N H O An enamine-H 2 O N OH N + O An enamine N O OH N O N O H H + H +-H 2 O H + 66 Imine vs. Enamine O N H NH 2 77 Enamines – Alkylation • The value of enamines is that the β-carbon is nucleophilic – enamines undergo SN2 reactions with methyl and 1° haloalkanes, α- haloketones, and α-haloesters – treatment of the enamine with one equivalent of an alkylating agent gives an iminium halide An iminium bromide (racemic) The morpholine enamine of cyclohexanone + Br •• N O Br S N 2 N O 3-Bromopropene (Allyl bromide) 88 Enamines - Alkylation – hydrolysis of the iminium halide gives an alkylated aldehyde or ketone Morpholinium chloride 2- Allylcyclo- hexanone + C l / H 2 + r- O O + l- N O 99 Enamines – Alkylation N CH 3 CCl O Cl- N O HCl O O N H H Cl- + Acetyl chloride An iminium chloride (racemic) 2-Acetylcyclo- hexanone (racemic) + + + H 2 O – enamines undergo acylation when treated with acid chlorides and acid anhydrides 1010 Malonic Ester Synthesis O EtOC CH 2 COEt O O R R CHCOH R CH...
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This note was uploaded on 06/12/2010 for the course CHEM 261 taught by Professor Austell during the Spring '08 term at UNC.

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Chapter 19-3 - 11 CHEM 262 Wei You Chapter 19 Enolate...

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