difunctional carbonyl compounds

difunctional carbonyl compounds - Difunctional Carbonyl...

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Difunctional Carbonyl Chemistry This guide to the lecture material and content of difunctional carbonyl chemistry has been broken up into several broad categories which have then been arranged by page. This should NOT be used instead of lecture material, or relied solely upon for information, and I take no responsibility for any errors contained herein. 1. Contents and Nomenclature 2. Introduction to dicarbonyl chemistry Why use dicarbonyls? 2. Methods of building 1,3-dicarbonyls Claisen Condensation Aldol 3. Alkylation of dicarbonyls Umpolung Decarboxylation of 1,3-dicarbonyls Ring synthesis Selective Alkylation Enone Synthesis 5. Kinetic vs. Thermodynamic product Reduction of enones 7. Synthesising 1,5-dicarbonyls β-haloketones Enones 8. Building 1,4-dicarbonyls Nitro compounds Nef Reaction Epoxide rings α-bromoketones 10. Ways of making 1,2-dicarbonyls Osmylation at alkenes Epoxide rings Pinnacol reaction Benzoin condensation 11. Other important reactions Ozonolysis γ,δ-Enones – Formation and re-arrangement Important Nomenclature before beginning The left diagram shows the nomenclature that you should properly familiarise yourself with before reading this document. In the case of calling carbons alpha, beta or gamma, I will use their Greek letter counterparts; α, β, and γ- carbons. H O alpha beta gamma H O 1 2 3 4
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Why use dicarbonyls? Dicarbonyls are useful because they may form enolates and enols with a more stabilised negative charge. This means that reactions that would need much more forcing conditions in a monocarbonyl compound need only weak bases in a dicarbonyl. EtO O O O NaEtO EtOH NaEtO EtOH pKa ~25 pKa ~9 EtO O O O 0.00001% 99.9999999% With a pKa of 18, EtO - will easily deprotonate the dicarbonyl group, but will barely deprotonate any of the ester. This means that in equilibria such as the one set up above, under fair conditions it is possible to make the reactive enolate species in a dicarbonyl. It is then easy to remove the dicarbonyl group by conversion to a carboxylic acid and decarboxylation. Methods of building 1,3-dicarbonyls Claisen Condensation The key thing to realise in using Claisen is that the carbonyl which is being attacked must contain an adequate leaving group, else aldol reaction will proceed. EtO
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This note was uploaded on 02/25/2012 for the course BIO 3410 taught by Professor Staff during the Spring '10 term at Texas State.

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difunctional carbonyl compounds - Difunctional Carbonyl...

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