1. Chapter 20 Enolates / other Carbanions
Organic Chemistry II
Fall 1999
Chapter 20 Enolates / other Carbanions
tautomer equilibrium:  859 Table 20.1
acidic/basic mechanism:  Figure
acidity of a-protons:  861 middle & 861 top
bases to produce enolates:  861 bot. & NaOEt
practice:  861 Problem 20.1
OrgChem-Chap20
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2. Alkylation of Enolates
Organic Chemistry II
Fall 1999
Alkylation of Enolates
leaving group
(L-)
nucleophile
(Nu:-)
electrophile
(R-L)
(Nu-R) d+ d-
SN2 reactions
SN2 reactions:  864 bottom & 865 bottom
use of bulky bases (LDA): no addition to carbonyls
practice:  866 Problem 20.5
OrgChem-Chap20
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3. Halogenation of the a-Carbon
Organic Chemistry II
Fall 1999
Halogenation of the a-Carbon
a-substitution: neutral,  862 bottom
faster with acid:  862 bot. & 863 top
basic conditions:  863 middle
haloform reaction: one-carbon elimination;  863 bottom & 864 top
terminal groups: CH3C(O)- & CH3CH(OH)-
OrgChem-Chap20
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4. More Stabilized Enolates
Organic Chemistry II
Fall 1999
More Stabilized Enolates
better Nu: & easier to generate the anions
synthetic equivalents: acetone anion ( 868), acetic acid anion ( 869)
dialkylation & other reactions:  870 
acetoacetate
malonate
p. 351
p. 364
OrgChem-Chap20
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5. Aldol Condensation self-condensation: b-hydroxy aldehyde
Organic Chemistry II
Fall 1999
Aldol Condensation
self-condensation: b-hydroxy aldehyde
addition to carbonyl:  873 Figure 20.3
dehydration: under vigorous conditions
stable a,b-unsaturated aldehyde:  874
diketones & mixed aldols:  876 & 877
reverse aldol in vivo:  Focus On
practice:  879 Problem 20.13
OrgChem-Chap20
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6. Chapters 18-19 Additions to the Carbonyls
Organic Chemistry II
Fall 1999
Chapters Additions to the Carbonyls
OrgChem-Chap20
Chapter 16

7. Ester Condensation Claisen condensation: b-ketoester
Organic Chemistry II
Fall 1999
Ester Condensation
Claisen condensation: b-ketoester
equilibrium controlled:  882 Figure 20.4
a,a-dialkyester: strong base only,  882 & 883
Dieckmann condensation:  883 middle
mixed Claisen condensation:  884
Cannizzaro reaction: no a-Hs;  888 Figure 20.5
practice:  886 Problem 20.18
OrgChem-Chap20
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8. Other Carbon Nucleophiles (I)
Organic Chemistry II
Fall 1999
Other Carbon Nucleophiles (I)
enamines: weak enolate equivalent
preparation: regioselectivity, 890 &  889 bot.
reactive E+ required:  890 top &  890 bottom
anion of dithianes: acyl anion equivalent
preparation & acidity: pKa = 31,  891
umpolung (polarity inversion): removal,  892
OrgChem-Chap20
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9. Other Carbon Nucleophiles (II)
Organic Chemistry II
Fall 1999
Other Carbon Nucleophiles (II)
dianions: two anions with different reactivity
preparation: strong bases,  892 bottom top
practice: 893 Problem 20.24
conjugate addition: a,b-unsaturated carbonyls
1,4-addition (Michael reaction): Figure 20.6 &  894
Robinson annulation: Michael / aldol,  896 bottom
2-cyclohexenones
OrgChem-Chap20
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10. Synthesis & Retrosynthesis
Organic Chemistry II
Fall 1999
Synthesis & Retrosynthesis
disconnection approach: retrosynthetic analysis
retrosynthetic arrow: target starting
recognition of functional groups: carbonyls
alkyl groups (enolates) mono/dicarbonyls:  898-9
b-hydroxy/a,b-unsaturated carbonyls aldol:  899 middle
1,3-dicarbonyls Claisen/aklyation:  899 middle
1,5-dicarbonyls Michael addition:  899 bottom
2-cyclohexenone Robinson anuulation:  900 top
practice:  & 901 Problem 20.29
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