Chapter 13: ethers & epoxides ; thiols & sulfides

Willamson ether synthesis

1) NaH

2) RX

Willamson ether synthesis mech

.

alkoxymercuration-demercuration

1) Hg(Oac)₂, ROH

2)NaBH₄

Acidic cleavage of an ether

excess Hx, heat

acidic cleavage of an ether mech

.

preparation of epoxides

MCPBA

or 1) Br_2, H₂O 2) NaOH

preparation of epoxides mechanism

.

Enantioselective epoxidation

.

Sharpless asymmetric epoxidation. +DET forms epoxide ____, -DET forms epoxide ____

Above, below

Epoxide ring opening with a strong nucleophile mech

.

Unsymmetrical epoxide opening. Where does nuc attack?

Nucleophile attacks at least sub

Symmetrical epoxide ring opening. what is observed?

Inversion of configuration is observed

Epoxide ring opening: Adding OR group

1) NaOR

2) H3O

Epoxide ring opening: Adding CN group

1) NaCN

2) H3O

Epoxide ring opening: Adding SR

1) NaSR

2)H3O

Epoxide ring opening: Using Grignard

1)RMgBR

2)H3O

Epoxide ring opening: Adding H

1)LiAlH4

2)H3O

Acid Catalyzed Ring Opening

HX

Acid Catalyzed ring opening of epoxide mech

.

Ring opening of epoxides: using water mech

.

Ring opening of epoxides using water

1) [H2SO4]

2) H2O

Ring Opening degree of substitution: 1° vs 2°. Where does the nuc attack?

Less hindered primary position

Ring Opening degree of substitution: 1° vs 3°. Where does the nuc attack?

tertiary position, because of the electronic effect.

Preparing thiols using SN2

NaSH

Preparing Sulfides

1)NaOH

2)RX

preparing sulfides from thiols mech

.

oxidation of thiols to disulfides

NaOH, Br₂

formation of disulfides mech

.

reduction of disulfides to thiols

HCl, Zn

Sulfide to sulfoxide

NaIO₄

sulfide to sulfone

2 H₂O₂