1. Stabilized Carbanions with One -M (I)
Organic Chemistry of Fine Chemicals
Spring 2006
Stabilized Carbanions with One -M (I)
Much weaker acid: pKa (RNO2: 9-10)
stronger base required: LiNR2 (LDA, LHMDS, KHMDS), NaH
Alkylation:  73 bottom
self-condensation:
(RCHO & RCOR’)
100% enolate formation & no equilibrium  74 middle
regioselectivity: kinetic vs thermodynamic enolates
 74 bottom-kinetic;  75 top-kinetic vs thermodynamic
nitroalkanes: O-alkylation;  75 bottom
OCFC-Chapter 5-2
Chapter 5-2

2. Condensation Reactions: Mechanism [Ch. 18]
Organic Chemistry of Fine Chemicals
Spring 2006
Condensation Reactions: Mechanism [Ch. 18]
OCFC-Chapter 5-2
Chapter 5-2

3. Stabilized Carbanions with One -M (II)
Organic Chemistry of Fine Chemicals
Spring 2006
Stabilized Carbanions with One -M (II)
Acylation: little explored,  76 top
preparation of b-keto carbonyl derivatives
alkylation of 1,3-dicarbonyl compounds: section 5.1.1
Claisen condensation: esters as acylating agents,  76 middle
weak base is enough: RO-;  76 bottom
not applicable to R2CH CO2R’:  77 top
unsymmetrical ketones: at the less substituted carbon;  77 middle
OCFC-Chapter 5-2
Chapter 5-2

4. Indirect Routes to a-Alkylation
Organic Chemistry of Fine Chemicals
Spring 2006
Indirect Routes to a-Alkylation
a-Alkylated aldehydes: condensation
conversion of aldehydes into unreactive functional groups
imines:  78 top (5.17)
1,3-oxazines:  78 bottom (5.18 & 19) &  79 top (5.20)
a-Alkylated ketones: regioselectivity (specific enolates)
b-keto carbonyls: selective a- or g-alkylation;  80 top
a,b-unsaturated ketones: dissolving metal reduction  80 bottom, or conjugate addition of carbanions;  81 top
OCFC-Chapter 5-2
Chapter 5-2

5. Organic Chemistry of Fine Chemicals
Spring 2006
Condensations (I)
Self-condensation:  81 middle & bottom reactions
aldol reaction followed by elimination of water
Mixed-condensation: RCH2CHO + R’CH2CHO
statistical reaction: four possible products,  82 top
most electrophilic carbonyls + most acidic a-hydrogen
aryl aldehydes (no a-hydrogen) + ketones, esters, nitroalkanes, anhydrides:  82 bottom & 83 top
aryl aldehydes + other aldehydes:  83 middle
OCFC-Chapter 5-2
Chapter 5-2

6. Organic Chemistry of Fine Chemicals
Spring 2006
Condensations (II)
How to prepare R2C=CRCHO:
indirect methods
the carbanions of imines:  83 bottom
the carbanions of 1,3-oxazine:  83 bottommost
the carbanions of ethoxyethyne:  84 top
100% enolate anion of esters:  84 bottom
Michael reactions: rare
nitroalkanes & acrylonitrile:  85 top
OCFC-Chapter 5-2
Chapter 5-2