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Unformatted text preview: 599 ESTER ENOLATES 21.29 The ﬁrst task is to convert acetic acid to ethyl chloroacetate.
O O O
Cl2 CH3COH ClCH2COH P Acetic acid CH3CH2OH
H ClCH2COCH2CH3 Chloroacetic
acid Ethyl chloroacetate Chlorination must precede esteriﬁcation, because the Hell–Volhard–Zelinsky reaction requires a
carboxylic acid, not an ester, as the starting material. The remaining step is a nucleophilic substitution reaction.
NaCN ClCH2COCH2CH3 N Ethyl chloroacetate 21.30 CCH2COCH2CH3
Ethyl cyanoacetate From the hint given in the problem, it can be seen that synthesis of 2-methyl-2-propyl-1,3-propanediol is required. This diol is obtained by a sequence involving dialkylation of diethyl malonate.
O CH3CH2CH2 CH2OCNH2 CH3CH2CH2 CH2OCNH2 H3C C
H3C CH2OH CH3CH2CH2 CH2OH H3C C CO2CH2CH3
Begin the synthesis by dialkylation of diethyl malonate. CH2(COOCH2CH3)2 1. CH3CH2CH2Br,
NaOCH2CH3 CH3CH2CH2 COOCH2CH3
C 2. CH3Br, NaOCH2CH3 COOCH2CH3 H3C
Diethyl malonate Diethyl 2-methyl-2-propylmalonate Convert the ester functions to primary alcohols by reduction.
C 1. LiAlH4 CH3CH2CH2
C 2. H2O COOCH2CH3 H3C CH2OH
CH2OH H3C Diethyl 2-methyl-2-propylmalonate 2-Methyl-2-propyl-1,3-propanediol Conversion of the primary alcohol groups to carbamate esters completes the synthesis.
C H3C 1. COCl2 CH3CH2CH2 2. NH3, H2O CH2OH CH2OCNH2
C H3C CH2OCNH2
O 2-Methyl-2-propyl-1,3-propanediol 21.31 Back Forward Meprobamate The compound given in the problem contains three functionalities that can undergo acid-catalyzed
hydrolysis: an acetal and two equivalent ester groups. Hydrolysis yields 3-oxo-1,1-cyclobutanedicarboxylic acid and 2 moles each of methanol and 2-propanol. The hydrolysis product is a malonic Main Menu TOC Study Guide TOC Student OLC MHHE Website ...
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- Fall '01
- Organic chemistry