lecture 19.2

lecture 19.2 - 19-19-1Organic Organic...

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Unformatted text preview: 19-19-1Organic Organic ChemistryChemistryWilliam H. BrownWilliam H. BrownChristopher S. FooteChristopher S. FooteBrent L. IversonBrent L. Iverson19-19-2Enolate AnionsEnolate AnionsChapter 19Chapter 1919-19-3Crossed Claisen CondsnsCrossed Claisen CondsnsCrossed Claisen condensations between two different esters, each with -hydrogens, give mixtures of products and are not usefuluseful crossed Claisen condensations are possible, however, if there is an appreciable difference in reactivity between the two esters; that is, when one of them has no -hydrogensOHCOEtEtOCOEtOCOEtOOEtOC-COEtDiethyl ethanedioate (Diethyl oxalate)DiethylcarbonateEthylformateEthyl benzoateO19-19-4Crossed Claisen CondsnsCrossed Claisen Condsnsthe ester with no -hydrogens is generally used in excessPhOCH3OOCH3O1. CH3O- Na+2. H2O, HClPhOCH3OOMethylpropanoateMethylbenzoate+Methyl 2-methyl-3-oxo-3-phenylpropanoate(racemic)19-19-5Claisen CondensationClaisen CondensationClaisen condensations are a route to ketonesOEtOOEtOO1. Et O- Na+2. H2O, HCl3. NaOH, H2O, heatOEtOO4. H2O, HCl5. heatOOHOOCO2OHOOEt OHEt OH++Reactions 1 & 2: Claisen condensation followed by acidificationReactions 3 & 4: Saponification and acidificationReaction 5: thermal decarboxylation+19-19-6Claisen CondensationClaisen CondensationThe result of Claisen condensation, saponification, acidification, and decarboxylation is a ketoneR-CH2-COR'OROCH2-C-OR'R-CH2-C-CH2-RO2HOR'CO2++severalsteps+from the esterfurnishing theenolate anionfrom the esterfurnishing the carbonyl group19-...
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lecture 19.2 - 19-19-1Organic Organic...

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