Chapter 19 Flashcards
despite their charge distribution, enolate anions react as … that create new … bonds, making enolate anions important for organic synthesis
carbon nucleophiles; C-C bonds
enolate anions react with haloalkanes in … reactions
SN2
in the aldol reaction, enolate anions derived from aldehydes or ketones react with a second molecule of … or … to give a … rxn and create a new C-C bond
aldehyde; ketone; carbonyl addition reaction
the mechanism of the base-catalyzed aldol rxns involves initial deprotonation of the alpha-H in base to create an … anion, which attacks another aldehyde or ketone molecule to give a carbonyl addition intermediate which in turn reacts with … to create a … produce and regenerates the original base
enolate; water; beta-hydroxy aldehyde or ketone
the mechanism of the acid-catalyzed aldol rxn involves an initial acid-catalyzed … to provide the … form; protonation of a second molecule on the carbonyl oxygen creates an electrophilic oxonium ion that is then attacked by the nucleophlic enol, followed by loss of a … to give the … product
keto-enol tautomerization; enol; proton; beta-hydroxy aldehyde or ketone
the beta-hydroxy aldehyde/ketone products of aldol rxns are easily dehydrated and lose H2O to give an …
alpha, beta-unsaturated aldehyde/ketone
the claisen condensation involves two ester molecules reacting in base to give a
beta-ketoester product
a dieckmann condensation is an … of a diester
intramolecular Claisen condensation
to become skilled at retrosynthetic analysis, it is important to recognize that the … and … functional groups are the characterstic products of an aldol rxn
alpha beta-unsaturated carbonyl; beta-hydroxy carbonyl
for retrosynthetic analysis, the … functional group is the characteristic product of claisen/dieckmann
beta-ketoester
enamines are formed through rxn of an aldehyde/ketone with a ..
secondary amine
enamines are important for synthesis bc the … is a nucleophile by virtue of conjugation of the C=C bond with the electron pair on nitrogen
beta-C
enamines resemble … and … in their rxns; yet harsh conditions are not required
enols; enolate anions
enamines can be alkylated on the beta c in an … rxn with … and …
SN2; methyl; primary haloalkanes
enamines can be acylated on the b-C by treatment with … and …
acid chlorides; acid anhydrides
the acetoacetic ester synthesis consists of 5 synthetic steps: ‘
ethyl acetoacetate is converted to its … anion using one equivalent of a base like sodium alkoxide the anion is used as a nucleophile in an SN2 rxn with … or …., …, and ..
the alkylated acetoacetic ester is … using OH-
acidification gives the …
heating causes … to give the alkylated … product
enolate; methyl; primary haloalkanes; alpha-haloketones; alpha-haloesters; hydrolyzed; alkylated acetoacetic acid; decarboxylation; ketone
For retrosynthetic analysis, a … is a characteristic product of the acetoacetic ester synthesis starting with ethyl acetoacetate, and other complex ketones can be derived from other b-ketoester starting materials.
methyl ketone
the acetoacetic ester synthesis is useful for synthesizing … and …
monosubstituted; disubstituted acetones
Malonic ester synthesis consists of 5 steps:
diethyl malonate is converted to its … anion using one equiv of sodium ethoxide
the anion is used as a nucleophile in an sn2 rx with … or …, …, and …
the alkylated acetoacetic ester is … using OH-
acidification gives the …
heating causes decarboxylation to give the … product
enolate; methyl; primary haloalkanes; alpha-haloketones; alpha-haloesters; hydrolyzed; alkylated acetoacetic acid; alkylated carboxylic acid
For retrosynthetic analysis, a … with one or two… bonded to the a-carbon is a characteristic product of the acetoacetic ester synthesis starting with diethyl malonate.
carboxylic acid; alkyl groups
in a Michael reaction, the .. carbon of a … species is electrophilic and able to react with certain nucleophiles, especially enolates
beta carbon; alpha beta unsaturated carbonyl specis
The mechanism of the Michael reaction involves initial formation of an …in base and attack of the enolate nucleophile onto the…of the Michael acceptor to create a new resonance-stabilized …that is protonated on oxygen to create an …and regenerate the base; then …. completes the reaction.
enolate anion; b-carbon; enolate anion intermediate; enol; tautomerization to the keto form
A Robinson annulation is a Michael reaction with an a,b-unsaturated ketone followed by an intramolecular… creating a … product.
aldol reaction; cyclic
….undergo conjugate addition with a,b-unsaturated carbonyl compounds in a reaction that is closely related to the Michael reaction.
Gilman reagents
Lithium diisopropylamide (LDA) is an extremely strong base that is not ….due to steric hindrance
nucleophilic
One molar equivalent of LDA converts aldehydes, ketones, and esters completely to their …
enolate anions.
If a slight excess of LDA is used, no equilibrium is established among the alternative enolate anions and the predominant enolate is the one that … (the removed a-hydrogen is more …). If a slight excess of carbonyl species is used, an equilibrium is set up in which the more …of the alternative enolate anions predominates, a situation known as thermodynamic control
forms more rapidly; accessible; stable
