Some Useful Synthetic Methods
more info: Classic Organic Reactions || Name Reactions 1  || Name Reactions 2 || Name Reactions 3 ||

Bond Formed
<retron>

Reaction Type

Example

C-H

Defunctionalization

Catalytic hydrogenation of an alkene (or alkyne).
Hydrogen atoms go on syn this has stereochemical implications for alkynes, cyclic alkenes and prochiral alkenes.


Clemmensen reduction


Wolff-Kishner reduction

"" with N2H4, KOH


Decarboxylation of a beta-ketoacid.
Acidifying groups besides carbonyl (keto) groups will decarboxylate.


Dissolving metal reduction of an alkyne



Dissolving metal reduction of an aromatic (Birch Reduction)


C-C
Homologation

SN2 displacement by cyanide
then CN > COH or CO2H or  C-NH2 or aldehyde
OTs instead of Br was used as an example because alcohol functionality has more 'synthetic continuity'



SN2 displacement by acetylide anion



Addition by Grignard reagent
(don't overuse this reaction!) If the organochloride or bromide is not commercially available and cheap, don't make Grignard reagents with them! Carbanion chemistry is best done with sp and sp2 carbon atoms.sp2 centers are generated more efficiently  by X / Li exchange.



NOTE: SN2 displacement by carbanions more basic than alkynide need special conditions.



carbanions of many varieties have been used to open epoxides.



Conjugate addition to an a,b-unsaturatedcarbonyl RCuLi group

Michael reaction
 (primarily)

Aldol reaction

Alkylation of ketone enolate anion
 like above electrophile eg. CH3-I

Malonic ester synthesis

Acetoacetic ester synthesis
 similar to above (see literature for details)


Friedel-Crafts acylation



Friedel-Crafts alkylation



Diels-Alder reaction
(the argument gets more interesting when intramolecular)



3,3-sigmatropic rearrangement

the retron for use is crowded C-C with stereochemical issues

C=C
Homologation

 Dehydrohalogenation  



Dehydration
(also of aldol products, see above)



 Hoffman elimination (NR3 and F-)



Wittig reaction
(also the related Peterson Olefination)



Tebby-type reagents


C-X
Free-radical halogenation  


Addition of H-X across C=C

Addition of X2 across C=C

Conversion of an alcohol to an alky halide or a sulfonate (activation toward elimination or substitution)

Hell-Volhard-Zelinski reaction  (alpha-halogenation of carboxylic acid)
C-OH 
Hydration of an alkene    


Hydroboration-oxidation

Grignard/ organo lithium reaction of an aldehyde or ketone
(1,2-addition)

Grignard reaction of an ester (tertiary alcohol)

Metal hydride reduction of an aldehyde, ketone or ester (complex stereochemical argument involved with this subject)

Aldol Reaction
 (see above)

metal-based reduction of ketone, aldehyde, or carboxylic acid derivative
C=O 
 Hydrolysis of an acetal/ ketal/ thioketal

Hydrolysis of an alkyne

Friedel-Crafts acylation             


Pinacol rearrangement
(stereochemistry in migrating groups can be important)

Claisen rearrangement (shown is the ester enolate Claisen)

oxy-Cope rearrangement
CO2H
 Hydrolysis of a carboxylic acid derivative CO2X where X = Cl, OR, OAc, NR.,, SR  OH, nitrile     


Oxidation of a primary or secondary alcohol
(Swern or Moffet)

Beckmann rearrangement 


Baeyer-Villiger oxidation