orgo 2 exam 4 part 2

what is claisen condensation

reaction of 2 esters to form a beta keto ester

what time of ester does claisen condensation not work with

R2CHCO2R type

what type of alkoxide should be used in claisen condensation

use what is at the end of the ester so OCH3 use methoxide OCH2CH3 use ethoxide because they are acyl compounds and they can undergo acyl sub reactions

what is dieckmann condensation

intramolecular claisen condensation to form cyclic beta keto este in a 5 or 6 member

what reagents to use for mixed claisen condensation

using nucleophile that can only serve as nuc and electrophile that can only serve as elec

acylation of enolates

beta dicarbonyl compounds from esters and ketones

alkylation of enolates

only primary alkyl halides can be used because enolates are strong bases

challenge with alkylation of enolates

if enolates is unsymmetrical, even though there are kinetic and thermodynamic enolates there is still going to be a mixture of products

what are viable electrophiles with alkylation of beta-dicarbonyl enolates

methyl, primary, and unhindered secondary alkyl halides

acetoacetic ester synthesis

phase 1- alkylation of acetoacetic ester and phase 2- hydrolysis and decarboxylation reveals ketone

malonic ester synthesis

phase 1- alkylation of malonic ester and phase 2- hydrolysis and decarboxylation leads to carboxylic acid

haloform reaction

starting material is one carbon has to be methyl group and other has to not have any alpha hydrogens and is added under dihalogen with base conditions leading to carboxylate anion followed by protonation of the carboxylic acid

how dies the haloform reaction work

base promoted halogenation which can happen outside of the haloform reaction but once one halogen is put it will keep getting put until there is no more halogens or hydrogen

what does the addition of 3 halogens to the alpha position do

sharply increases electrophilicity of the carbonyl

what happens when there are non more alpha protons

hydroxide acts as a nucleophile and adds to the carbonyl forming the tetrahedral intermediate and the intermediate breaks down to reform a carbonyl by forcing out the trihalomethyl anion forming a carboxylic acid that is immediately deprotonated

how many alpha-beta unsaturated compounds have of electrophilic carbons owing to electron delocalization

2

What is 1,2 addition based of also known as direct addition

kinetically controlled with strongly basic nucleophiles are electrostatically more attracted to carbonyl carbon and the reaction results in an alcohol while maintaining the alpha-beta unsaturation

what is 1,4 addition also known as conjugate addition

thermodynamically controlled with weakly basic nucleophiles adding to the beta position and result in an enolate intermediate which upon protonation maintains the carbonyl

what is the michael reaction

the addition of weakly basic enolate of a beta dicarbonyl compound to the beta position of an alpha beta unsaturated carbonyl compound and created a new compound with 1,5 relationship between carbonyls

what will lithium dialkyl cuprates do

alkylate at the beta position of an alpha beta unsaturated carbonyl compound

what does alpha beta unsaturation do

increases polarity because alpha and beta positions are sp2 hybridized so their chemical shifts are much further downfield but the trend between alpha and beta is opposite the trend of alpha and beta unsaturated

what type of reaction does Grignard and lithium do(RMgX, RLi, Nac triple bond CH or sodium acylelide)

1,2 additions because its a strong based and once they make a bond they can’t back out since they are terrible leaving groups

beta position

less polar than the carbonyl position its less electrostatically attractive to strongly basic compounds so types of nucleophiles that end up at the beta position are weakly basic

what reagents do 1,4 addition use

SR, cyanide, and X-

what is robison annulation

it is michael reaction and then intramolecular aldol