310_15 - Organic Lecture Series CH 310 N LECTURE 15...

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Organic Lecture Series 1 CH 310 N LECTURE 15 Textbook Assignment: Chapter 19 Enolates & Enamines Homework (for credit): Problem Set 5-Posted Today’s Topics: Active methylenes; Michael addn; Ring Rxns Notice & Announcements: EXAM 1: Pick up papers-Dr C’s office hrs Organic Lecture Series 2 Enolate Enolate Anions Anions and and Enamines Enamines Chapter 19
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Organic Lecture Series 3 Synthetic Advantages of Synthetic Advantages of Enamines Enamines vs vs Enolates Enolates 1) Avoids proton transfer. 2) Regiochemistry of alkylation can be controlled. (For un-symmetric ketones) 3) Avoids polyalkylation. 4) Avoids O-alkylation. Organic Lecture Series 4 O CH 3 O - CH 3 O - CH 3 Kinetic Enolate 1)"Less" Stable 2) Form with LDA H H B: :B Thermodynamic Enolate 1)"More" Stable 2) Form with OH - or OR - 3) Equilibrating conditions Kinetic vs Thermodynamic Enolates
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Organic Lecture Series 5 Polyalkylation Polyalkylation of of Enolates Enolates : Organic Lecture Series 6 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
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Organic Lecture Series 7 – consider the AAE synthesis of this target molecule, which is a monosubstituted acetone these three carbons are from ethyl acetoacetate the -R group of a monosubstituted acetone 5-Hexen-2-one O Acetoacetic Acetoacetic Ester Synthesis Ester Synthesis Organic Lecture Series 8 – Step 1: formation of the enolate anion of AAE – Step 2: alkylation with allyl bromide COOEt O Et O - Na + O + Et OH Sodium salt of ethyl acetoacetate Sodium ethoxide Eth ano l p K a 15.9
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This note was uploaded on 11/21/2011 for the course CH 51455 taught by Professor Colapret during the Spring '11 term at University of Texas at Austin.

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310_15 - Organic Lecture Series CH 310 N LECTURE 15...

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