318-19 - CH 318 N LECTURE 19 Textbook Assignment: Chapter...

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CH 318 N LECTURE 19 Textbook Assignment: Chapter 20 (omit sec 20.3) Homework (for credit): POW 10 posted Today’s Topics: Malonic ester synthesis; Michael addition & the Robinson Ring Annulation Notice & Announcements: New feature added to WEB site: “Dr. C’s Notebook” Organic Lecture Series 2 Enolate Anions Enolate Anions and and Enamines Enamines
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Organic Lecture Series 3 The acetoacetic ester (AAE) synthesis is useful for the preparation of mono- and disubstituted acetones of the following types CH 3 CC H 2 COEt O O R' 3 HR O 3 H 2 R O A disubstituted acetone A monosubstituted Ethyl acetoacetate (Acetoacetic ester) Acetoacetic Acetoacetic Ester Synthesis Ester Synthesis CCH 3 H 2 C CO 2 Et O These types of reactions involve active (i.e. acidic) methylene units as the nucleophilic component. Organic Lecture Series 4 • The strategy of a malonic ester (ME) synthesis is identical to that of an acetoacetic ester synthesis, except that the starting material is a β -diester rather than a β -ketoester O Et OC 2 O O R R CHCOH R 2 COH O acetic acid A monosubstituted acetic acid Diethyl malonate (Malonic ester) Malonic Malonic Ester Synthesis Ester Synthesis
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Organic Lecture Series 5 Consider the synthesis of this target molecule CO 2 Et H 2 C CO 2 Et MeO OH O 5-Methoxypentanoic acid These two carbons are from diethyl malonate Malonic Malonic Ester Synthesis Ester Synthesis MeO H 2 C C H 2 CH 2 X Organic Lecture Series 6 – treat malonic ester with an alkali metal alkoxide – alkylate with 1-bromo-3-methoxy propane COOEt Et O - Na + + + Et OH Eth ano l p K a 15.9 (weaker acid) Sodium ethoxide Sodium salt of diethyl malonate + Diethyl malonate p K a 13.3 (stronger acid) Br + + - + + S N 2 Malonic Malonic Ester Synthesis Ester Synthesis
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Organic Lecture Series 7 – saponify and acidify – decarboxylation 2EtOH + COOEt MeO 3. NaOH, H 2 O 4. HCl, H 2 O COOH MeO MeO heat CO 2 + 5-Methoxypentanoic acid Malonic Malonic Ester Synthesis Ester Synthesis Organic Lecture Series 8 3 3 3 Application: Synthesis of 4,4-Disubstituted Piperidines
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Organic Lecture Series 9 Application: Synthesis of 4,4-Disubstituted Piperidines CH 2 CN N Cl Cl CH 3 NaH NCH 3 Ph NC NCH 3 Ph HOOC
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318-19 - CH 318 N LECTURE 19 Textbook Assignment: Chapter...

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