Ethers, Sulfides and Epoxides

1
Ethers, Sulfides and Epoxides
chapter 11

• Structure, nomenclature, properties
• Ether synthesis - Williamson synthesis (SN2)
• H/ROH addition to 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)

blue - repeat of earlier chemistry
ss12 19
2
sources nomenclature properties reactions
substitution protecting groups epoxides epoxide
reaction
3
Ethers, Sulfides and Epoxides - 11
Structure - tetrahedral (sp3) oxygen carbon
4
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
5
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? Others? SN1, some cases
8
Ethers, Sulfides and Epoxides - 11
H/ROH addition to olefins, hydration-like
Familiar?
Recall/review addition problems 6.29, 6.34a
9
Ethers, Sulfides and Epoxides - 11

• Reactions - acid catalyzed cleavage of ethers

10
sources nomenclature properties reactions
substitution protecting groups epoxides epoxide
reaction
11
Ethers, Sulfides and Epoxides - 11
Ethers Protecting Groups (ref. problems 6.33)
Problem 6.33 alcohol interferes with Br2
addition
12
Ethers, Sulfides and Epoxides - 11
Ether Protecting Groups (ref. problems 6.33)
3
1
2
Problem 6.33 alcohol interferes with Br2
addition
protecting group (Pg) blocking group
13
Ethers, Sulfides and Epoxides - 11
Protecting groups characteristics
3
1

• On efficient
• Inert to rx
• Off efficient

2
Problem 6.33 alcohol interfers with Br2
addition.
protecting group (Pg) blocking group
14
Ethers, Sulfides and Epoxides - 11
TMS ethers
15
Ethers, Sulfides and Epoxides - 11
16
Crown Ethers - not covered

• 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

O
O
O
O
O
O
17
Ethers, Sulfides and Epoxides - 11
Nomenclature - epoxy (substituent) or oxirane
ether
4,5-epoxycycloheptene
(4S,5R)-4,5-epoxycycloheptene
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
Other sources of epoxides - halohydrins/base
chapter 6
22
Reactions of epoxides H or LA Opening
B or LB Opening
23
Reactions of epoxides H or LA Opening
mechanism?
24
Reactions of epoxides B or LB Opening
mechanism?
25
Stereochemistry
1,2-transdiol
26
Regioselectivity
SN2 like
27
Regioselectivity
SN1 like
28
Regioselectivity
29
example epoxyresin
30
Application of Epoxy Chemistry
31
Application of Epoxy Chemistry
32
Application of Epoxy Chemistry
33
Application of Epoxy Chemistry
34
Application of Epoxy Chemistry
35
(No Transcript)
36
lithium aluminum hydride
37
Organometallic Compounds (R-M)
Organomagnesium Organolithium compds 15.1
Lithium Diorganocopper (Gilman) Reagents 15.2
Not covered Organopalladium reagents, Heck
reaction, carbenes, carbenoids, alkene
metathesis.
Synthesis, Concepts and the Final