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Total Synthesis of Linoxepin through a Palladium-Catalyzed Domino Reaction Lutz F. Tietze Angew. Chem. Int. Ed. 2013, 52, 3191–3194 Speaker: 王湘閔
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outline Motivation Isolation and biological activities Retrosynthetic analysis Synthesis of Linoxepin Conclusion 1
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Motivation The novel lignan is an attractive synthetic goal. Biological profiles 2
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Isolation and biological activities In 2007, Schmidt and co-workers isolated a lignan from the aerial parts of Linum perenne L. They have long been used as herbal remedies for pain, herbal remedies for pain, rheumatoid arthritis, and warts. rheumatoid arthritis, and warts. 3
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Retrosynthetic analysis Sonogashira reaction/ Carbopalladation/Heck reaction 4
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Preparation of monomer 4 & 5 Synthesis of Linoxepin 5
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Preparation of domino precursor 2 Synthesis of Linoxepin 6
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Domino Sonogashira/carbopalladation/ Heck reaction Synthesis of Linoxepin 7
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Synthesis of linoxepin (1) Synthesis of Linoxepin 8
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Conclusion First total synthesis of (+)- and (-)-linoxepin ( 1 ) in only ten steps and an overall yield of 30% without the use of any protecting groups. Multiple Pd-catalyzed reactions: Sonogashira reaction Sonogashira reaction Domino carbopalladation/Heck reaction Domino carbopalladation/Heck reaction 9
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Total Synthesis of (+)- Linoxepin by Utilizing the Catellani Reaction Mark Lautens Angew. Chem. Int. Ed. 2013, 125, 5413–5416 Speaker: 王湘閔
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Outline Retrosynthetic analysis Synthesis of (+)-Linoxepin Conclusion Summary 11
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Retrosynthetic analysis Palladium-catalyzed Catellani reaction 12
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Synthesis of the monomers Synthesis of Linoxepin 13
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Key step: Catellani reaction Catellani reaction oxidative addition base-mediated C-H activation carbopalladation oxidative addition reductive elimination transmetalation reductive elimination retro carbopalladation Mizoroki-Heck type reaction 14
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Attempted synthesis of (±)-linoxepin (1) Synthesis of Linoxepin 15
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Undesired formation of (±)- iso -linoxepin (14) Synthesis of Linoxepin 16
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Mechanistic rationale for the formation of (±)-1 and (±)-14 Synthesis of Linoxepin syn -hydride elimination via Pd-enolate formal anti -hydride elimination syn -hydride elimination reductive elimination 17
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Synthesis of (+)-linoxepin (1) Synthesis of Linoxepin 18
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Conclusion First asymmetric synthesis of (+)-1 in eight steps and an overall yield of 30% without the use of any protecting groups. Key step: domino C-H functionalization palladium-catalyzed Catellani reaction palladium-catalyzed Catellani reaction 19
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Summary [a] D (CHCl 3 ) Key steps Steps/yield Nature product +23.0; c = 0.93, Angew. Chem. Int. Ed. 2013, 52, 3191–3194 +96.1; c = 0.61, Sonogashira reaction and a domino carbopalladation/Heck reaction of an allylsilane 10 steps, 30 % Angew. Chem. Int. Ed. 2013, 125, 5413–5416 +90.0; c = 0.25, domino C-H functionalization Catellani reaction 8 steps, 30 % 20
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