Ch. 23 Flashcards
Carbonyl Condenstion Reaction
Comprises two carbonyl partners and involves nucleophilic addition and alpha-substitution processes
- Carbonyl converted by base into a nucleophilic enolate ion (nucleophilic donor) = alpha-substitution
- Addtion of nucleophilic enolate ion to electrophilic carbonyl (electrophilic acceptor) = nucelophilic addition
Adol Reaction
reversible reaction that involves two aldehydes/ketones
- lead first to beta-hydroxy aldehyde/ketone
- then dehydrated to alpha,beta-unsaturated products
Claisen Condensation Reaction
Carbonyl condensation between two ester components that produces a beta-keto ester product; reversible, similar mechanism to aldol reaction
Dieckmann Cyclization Reactions
Intermolecular claisen condensations that yield fix/six-membered cyclic beta-keto esters starting from 1,6 and 1,7-diesters; similar to clasien condensation; product can be futher alkylated
1,6-Diesters form 5-membered rings
1,7-Diesters form 6-membered rings
Michael Reaction
Involves a conjugated additon of a carbon nucleophile (enolate) to an alpha,beta unsaturated acceptor/carbonyl compound
best rxns are between relatively acidic donors/stable enolates (beta-keto esters/beta-diketones) and unhindered alpha,beta-unsaturated acceptors/carbonyl compounds
Robinson Annulation Reaction
Comprises a Michael addition and an intramolecular aldol cyclization forming a substituted cyclohexenone (substituted ring systems)
- Michael additon by treatment of a beta-diketone/beta-ketone ester (nucleophilic donor) with an unsaturated ketone (acceptor);
1,5-diketone intermediate - Intramolecular aldol cyclization/condensation
What are the four common carbonyl group reactions?
Nucleophilic addition, nucleophilic acyl substituion, carbonyl alpha-substitution, and carbonyl condensation
Mixed Adol Condensation
Two different aldehydes/ketones; give mixture of four possible products (two self-condensation and two mixed products)
Intramolecular Aldol Condensations of 1,4 and 1,5-diketones
yield five/six-membered cyclic rings; more strain-free ring predominates
Mixed Claisen Condensation
only successful when one of the two partners have no acidic alpha-hydrogens (ex. ethyl benzoate/ethyl formate); only function as acceptor partner
What are good Michael donors?
Enamines; prepared by rxn of ketone with disubstituted amine (Stork Reaction)
Aldol Reaction Reagents (Regular, Mixed and Intramolecular)
NaOH, ethanol
Mixed Aldol Reaction Reactants
- PhCHO
2. CH2O
Dehydration of Aldol reagent
NaOH or H3O+
Claisen Condensation reagent (Regular, Mixed, and Intramolecular)
Na+ -OEt, ethanol
Mixed Claisen Condensation reactants
HC=OOEt
Michael Reaction Reagent
Na+ -OEt, ethanol
Carbonyl condensations with enamines reagents
- THF solvent
2. H3O+
What type of reaction is aldol condensation reaction?
base-catalyzed dimerization of two aldehydes/ketones
Does the equilbrium of aldehydes/ketones in aldol reaction favor the products or reactants?
Products
Dehydration of Aldol Products
yield alpha, beta-unsaturated aldehydes and ketones; catalyzed by both acid and base; slightly more severe than condensation
Are conjugated enones or nonconjugated enones more stable?
Conjugated enones are more stable
When can a mixed aldol reaction form a single product?
- one carbonyl component has no alpha-hydrogens
2. one carbonly compound is more acidic than the other
Mixed Claisen Condensation
- Two different esters with one component having no alpha hydrogens
- Ketone and ester with no alpha hydrogens
What are Michael donors and acceptors?
Stable enolates = Michael donors
Alpha,beta-unsaturated compounds = Michael acceptors
Stork Reaction
Ketone converted into an enamine to act as a Michael donor;
equivalent to Michael addition of ketone to yield a 1,5-diketone product
- Enamine formation to form ketone
- Michael-type addition to alpha,beta-unsaturated carbonyl compound
- Enamine hydrolysis back to ketone
