University:
Kentucky State University
Course:
CHE 302 | Organic Chemistry II
Academic year:

2023
Views:

424

Pages:

25
Author:

Apolenajz

Pharmaceutical organic chemistry “Epoxides” Lecture 7 Pharmaceutical organic chemistry “Epoxides” Lecture 7 Preparation of Epoxides Using a Peroxyacid • Treat an alkene with a peroxyacid Preparation of Epoxides Using a Peroxyacid • Treat an alkene with a peroxyacid Epoxides from Halohydrins • Addition of HO-X to an alkene gives a halohydrin • Treatment of a halohydrin with base gives an epoxide • Intramolecular Williamson ether synthesis Epoxides from Halohydrins • Addition of HO-X to an alkene gives a halohydrin • Treatment of a halohydrin with base gives an epoxide • Intramolecular Williamson ether synthesis Reactions of Epoxides: Ring-Opening • • • • Water adds to epoxides with dilute acid at room temperature Much milder conditions than ethers because of the ring strain Product is a 1,2-diol (on adjacent C’s: vicinal) Mechanism: acid protonates oxygen and water adds to opposite side (trans addition) Reactions of Epoxides: Ring-Opening • • • • Water adds to epoxides with dilute acid at room temperature Much milder conditions than ethers because of the ring strain Product is a 1,2-diol (on adjacent C’s: vicinal) Mechanism: acid protonates oxygen and water adds to opposite side (trans addition) Reactions of Epoxides: Ring-Opening • • • • Water adds to epoxides with dilute acid at room temperature Much milder conditions than ethers because of the ring strain Product is a 1,2-diol (on adjacent C’s: vicinal) Mechanism: acid protonates oxygen and water adds to opposite side (trans addition) Reactions of Epoxides: Ring-Opening • • • • Water adds to epoxides with dilute acid at room temperature Much milder conditions than ethers because of the ring strain Product is a 1,2-diol (on adjacent C’s: vicinal) Mechanism: acid protonates oxygen and water adds to opposite side (trans addition) Halohydrins from Epoxides • Anhydrous HF, HBr, HCl, or HI combines with an epoxide Halohydrins from Epoxides • Anhydrous HF, HBr, HCl, or HI combines with an epoxide Regiochemistry of Acid-Catalyzed Opening of Epoxides • Nucleophile preferably adds to less hindered site if primary and secondary C’s • Also at tertiary because of carbocation character Regiochemistry of Acid-Catalyzed Opening of Epoxides • Nucleophile preferably adds to less hindered site if primary and secondary C’s • Also at tertiary because of carbocation character Regiochemistry of Acid-Catalyzed Opening of Epoxides • Nucleophile preferably adds to less hindered site if primary and secondary C’s • Also at tertiary because of carbocation character Regiochemistry of Acid-Catalyzed Opening of Epoxides • Nucleophile preferably adds to less hindered site if primary and secondary C’s • Also at tertiary because of carbocation character Regiochemistry of Acid-Catalyzed Opening of Epoxides • Nucleophile preferably adds to less hindered site if primary and secondary C’s • Also at tertiary because of carbocation character Base-Catalyzed Epoxide Opening • Strain of the three-membered ring is relieved on ring-opening • Hydroxide cleaves epoxides at elevated temperatures to give trans 1,2-diols Base-Catalyzed Epoxide Opening • Strain of the three-membered ring is relieved on ring-opening • Hydroxide cleaves epoxides at elevated temperatures to give trans 1,2-diols Addition of Grignards to Ethylene Oxide • Adds –CH2CH2OH to the Grignard reagent’s hydrocarbon chain • Acyclic and other larger ring ethers do not react Addition of Grignards to Ethylene Oxide • Adds –CH2CH2OH to the Grignard reagent’s hydrocarbon chain • Acyclic and other larger ring ethers do not react Addition of Grignards to Ethylene Oxide • Adds –CH2CH2OH to the Grignard reagent’s hydrocarbon chain • Acyclic and other larger ring ethers do not react Addition of Grignards to Ethylene Oxide • Adds –CH2CH2OH to the Grignard reagent’s hydrocarbon chain • Acyclic and other larger ring ethers do not react Reduction of Epoxide • Lithium Aluminum Hydride (LiAlH4) or sodium borohydride (NaBH4) can be used to reduce epoxides to alcohols OH O 1, LiAlH4, Ether 2. H3O+ OH O 1, LiAlH4, Ether 2. H3O+ Reduction of Epoxide • Lithium Aluminum Hydride (LiAlH4) or sodium borohydride (NaBH4) can be used to reduce epoxides to alcohols OH O 1, LiAlH4, Ether 2. H3O+ OH O 1, LiAlH4, Ether 2. H3O+

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