Chapter 18 (Lecture #20)

Chapter 18 (Lecture #20) - The Malonic Ester Synthesis of...

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The Malonic Ester Synthesis of Substituted Acetic Acids By a similar sequence of alkylation, hydrolysis, and decarboxylation, substituted acetic acids may be prepared from diethyl malonate . EtOCCH 2 COEt O = O R- CH 2 COOH diethyl malonate alkylated acetic acid malonic ester synthesis
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The Malonic Ester Synthesis EtOCCH 2 COEt O = O diethyl malonate (pK a = 12.9) + NaOEt EtOCCHCOEt O O - Na + + EtOH pK a = 16 enolate anion (stoichiometric amount) formation of enolate anion alkylation EtOCCHCOEt O O - Na + + R-X EtOCCHCOEt O O R + NaX alkylated malonic ester EtOCCHCOEt O O R hydrolysis (i) dil. NaOH, heat (ii) H 3 O + HOCCHCOH O O R alkylated malonic acid HOCCHCOH O O R decarboxylation heat (-CO 2 ) R- CH 2 COOH "alkylated acetic acid"
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An Example of a Two-Stage Alkylation Scheme EtOCCH 2 COEt O = O 1 eq. NaOEt EtOCCHCOEt O O Na + EtOH - CH 3 I alkylation EtOCCHCOEt O O CH 3 - EtOCCHCOEt O O CH 3 1 eq. NaOEt EtOH EtOCCCOEt O O CH 3 Na + C 6 H 5 CH 2 Cl alkylation CH 3 C 6 H 5 CH 2 C-CO 2 Et CO 2 Et CH 3 C 6 H 5 CH 2 C-CO 2 Et CO 2 Et (i) dil. NaOH, heat
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Chapter 18 (Lecture #20) - The Malonic Ester Synthesis of...

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