Synthesis

Remember: Sodium Salts of Acetylenes

HC CH

NaNH2

NH3

HC CNa

HC CNa +1. NH3

2. H3O+

O HO C CH

(65-75%)

• What compound will be obtained from the reaction shown below?

•• A) B)

• C) D)

Question

CHCH3(CH2)3C + CH3CH2MgBr

CMgBrCH3(CH2)3C + CH3CH3

diethyl ether

1. H2C O2. H3O+

CCH2OHCH3(CH2)3C

(82%)

Using Acetylenic Grignard Reagents

• Consider the reaction below. Why won’t it work?

• The alcohol can act as an acid, especially in the presence of reactive reagents like the Grignard reagent.

• The alcohol must be protected to prevent it from reacting.

Protection of Alcohols

• A three-step process is required to achieve synthesis of the targeted diol.

Protection of Alcohols

There are many different “protecting” groups for each of the various functions.

Each must be easily added and easily removed.

http://en.wikipedia.org/wiki/Protecting_group

• The protection step requires the presence of a base.

Protection of Alcohols (TMS)

Protection of Alcohols

TMS is removed with H3O+ or with F–, which comes from TBAF.

H3O+ or

SEE: CONCEPTUAL CHECKPOINT 13.18

A. gB. hC.c, g, a, bD.c, h, a, bE. c, I, b

What is the correct order of reagents needed for the following transformation?

Question

• Thionyl chloride, SOCl2, has commonly been used to convert alcohols to an alkyl chlorides.

Reactions of Alcohols

A.

B.

C.

D.

OH

SOCl2

Cl

Cl

Cl

Cl Cl

pyridine

What is the product of the following reaction?

Question

• PBr3 can be used to convert an alcohol to an alkyl bromide.

• Note that the last step of the SOCl2 and PBr3 mechanisms are SN2 reactions.

• SEE: SKILLBUILDER 13.6

Reactions of Alcohols

A.

B.

C.

D.

OHPBr3

Br

Br

Br

Br

Br

What is the product of the following reaction?

Question

Oxidation-Reduction Reactions

SummaryReactions of Alcohols

Reactions Paths:to & from alcohols

Cl Br

OHA. 1) Hg(OAc)2, THF:H2O 2) NaBH4, OH– 3) TMS-Cl, Et3N

4) Potassium tert-butoxide 5) HBr/H2O2 6) TBAF

B. 1) NaBr/DMSO 2) Hg(OAc)2, THF:H2O 3) NaBH4, OH–

C. 1) Hg(OAc)2, THF:H2O 2) NaBH4, OH– 3) TMS-Cl, Et3N

4) Potassium tert-butoxide 5) BH3:THF 6) H2O2, OH– 7)

PBr3 8) TBAF

D. all of the above

What is the correct order of reagents needed for the following transformation?

Question