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Ethers, Sulfides and Epoxides - 11

Structure, nomenclature, properties Ether synthesis - Williamson synthesis ( S N 2 ) H + /ROH addition to olefins (chapt 6) Reactions - acid catalyzed cleavage of ethers ( S N 2/S N 1/E1 ) [oxidation out ] Ethers as Protecting Groups (Gps). Epoxides - oxirane nomenclature

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Ethers, Sulfides and Epoxides - 11

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  1. Structure, nomenclature, properties Ether synthesis - Williamson synthesis(SN2) H+/ROH additionto olefins (chapt 6) Reactions - acid catalyzed cleavage of ethers (SN2/SN1/E1) [oxidation out] Ethers as Protecting Groups (Gps). Epoxides - oxirane nomenclature Preparation: epoxidation,halohydrin Reactions - nucleophilic cleavage (SN2/SN1/E1) [sulfides out] Synthesis (continued) C H 3 C H 3 Ethers, Sulfides and Epoxides - 11 O H H [blue - repeat of earlier chemistry]

  2. diethyl ether tetrahydrofuran or THF dihydropyran Ethers, Sulfides and Epoxides - 11 Structure - tetrahedral (sp3) oxygen & carbon

  3. Ethers, Sulfides and Epoxides - 11 Nomenclature - ether group is a substituent 2-cyclopentenol 4-ethoxy-2-cyclopentenol (1S,4R)-4-ethoxy-2-cyclopenten-1-ol

  4. trans-2-propoxycyclohexanol 2-methyl-2-methoxypropane (t-butyl methyl ether) O H C H H C 3 3 C H H C 3 3 Nomenclature of Ethers O O C

  5. Hydrogen bond acceptor (Lewis base) Ethers, Sulfides and Epoxides - 11 Properties - polar C-O covalent bonds But low dielectric constant

  6. Ethers, Sulfides and Epoxides - 11 Two ways to prep benzyl ethyl ether Williamson ether synthesis SN2 substitution recall similar problems in chapter 9 (9.46, 9.48 and 9.49)

  7. Ethers, Sulfides and Epoxides - 11 Two ways benzyl ethyl ether can be prepared Specifically how would each be done? Nucleophic form of the alcohol? Solvent? - alkoxide - polar - aprotic - benzylic substrate Which way should be best?

  8. B r C H C H 3 3 C H O C C H O C C H C H B r 3 3 3 3 C H C H 3 3 Preparation of Ethers + O O + look at Problem 9.49b

  9. Ethers, Sulfides and Epoxides - 11 H+/ROH addition to olefins, “hydration-like” Recall/review addition problems 6.29, 6.34a

  10. Reactions - acid catalyzed cleavage of ethers Ethers, Sulfides and Epoxides - 11 SN2 SN1/E1

  11. Ethers, Sulfides and Epoxides - 11 Ethers Protecting Groups Problem 6.33: alcohol “interferes” with Br2 addition.

  12. Ethers, Sulfides and Epoxides - 11 Ether Protecting Groups 3 1 2 Problem 6.33: alcohol “interferes” with Br2 addition. Protecting group (Pg) = blocking group

  13. Ethers, Sulfides and Epoxides - 11 Protecting groupcharacteristics 3 1 Pg “Requirements” • On efficient • Inert to rx • Off efficient 2 Problem 6.33: alcohol “interferes” with Br2 addition. Protecting group (Pg) = blocking group

  14. trimethylsilyl ether or TMS ether Ethers, Sulfides and Epoxides - 11 TMSethers

  15. Cyclic polyethers The parent name is crown, preceded by a number describing the size of the ring followed by the number of oxygen atoms in the ring, e.g 18-crown-6 Crown Ethers - not covered O O O O O O

  16. Structure, nomenclature, properties of Ethers Preparation: Ether synthesis – Williamson Synthesis H+/ROH addition to olefins Reactions - acid catalyzed cleavage of ethers Ethers as Protecting Groups (Gps). Epoxides - nomenclature Preparation: epoxidation, halohydrin Reactions - nucleophilic cleavage C H 3 C H 3 Ethers, Sulfides and Epoxides – Chapter 11 O H H

  17. oxirane Ethers, Sulfides and Epoxides - 11 Nomenclature - epoxy (substituent) oroxirane ether 4,5-epoxycycloheptene (4S,5R)-4,5-epoxycycloheptene special 3-membered ring (ignore - not questioned) [ (3S,4S)-2-chloro-3,4-epoxyheptane ]

  18. Ethers, Sulfides and Epoxides - 11 Prep of epoxides/oxiranes

  19. Ethers, Sulfides and Epoxides - 11 Prep of epoxides - better mechanistic view stereospecific like bromine addition

  20. other epoxide sources - halohydrins/base mechanism intramolecular “SN2” See problem 9.50, same reaction

  21. :B Other sources of epoxides - halohydrins/base chapter 6

  22. Reactions H+ or Lewis Acid Opening of epoxides : B: or Lewis Base Opening

  23. Reactions H+ or Lewis Acid Opening of epoxides: mechanism?

  24. Reactions B: or Lewis Base Opening of epoxides: Mechanism?

  25. Recall: 1,2-cisdiol Stereochemistry 1,2-transdiol

  26. 3o more hindered 1o-less hindered proton source Regioselectivity SN2 like

  27. Regioselectivity SN1 like

  28. example epoxyresin

  29. Application of Epoxy Chemistry

  30. amine epoxide Application of Epoxy Chemistry

  31. Application of Epoxy Chemistry

  32. Application of Epoxy Chemistry

  33. Application of Epoxy Chemistry

  34. like sodium borohydride lithium aluminum hydride

  35. C H 3 H H C C H H O

  36. ethylene oxide is a valuable building block for organic synthesis because each of its carbons has a functional group Ethylene Oxide

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