Alkynes

Reaction

Acidity

Synthesis

Complex of Acetylene

Bonds

Hydrocarbon Comparison

Alkyne Nomenclature

HC CCH2CH2CH3

1-pentyne 4-decyne

CH2C C CH3

3-(2-butynyl)cyclohexene 5-phenyl-1-hepten-6-yne

Enes with Ynes

chain numbered from end closest to -bond

1 57

7,8-dimethyl-5(E),7(Z)-decadien-1-yne

tie goes to the alkene

Endiyne Antitumor Agents

HO cycloaromatizationHO

.

.

HO H abstraction

diradical

NH

O

O

OH

OH OH

CO2H

OCH3

CH3

O

Dynemycin AAntitumor antibiotic

O

OO

O

O

CH3

OCH3HO

O

OO

NHCH3

HO

HO

CH3

base:

O

CH3

OCH3OO

OO

NHCH3

HO

HO

CH3

OO

O

OHNCS-chrom

NCS-chrom

O

OO

O

O

CH3

OCH3O

O

OO

NHCH3

HO

HO

CH3

H

base:

OH

OO

O

O

CH3

OCH3OO

OO

NHCH3

HO

HO

CH3

H-base

OH

OO

O

O

CH3

OCH3OO

OO

NHCH3

HO

HO

CH3

O

CH3

OCH3OO

OO

NHCH3

HO

HO

CH3

OO

O

OH

.

.Diradical intermediate undergoes

H atom transfer with ribose backbone in DNA

Catalytic Hydrogenation

75 psi

H2 - 1%Pt on C

Lindlar’s Catalyst

H2 on a Poisoned Catalyst Prevents Over-Reduction

cis Alkenes

5-decyne

H2 / Pd on BaSO4

quinolineLindlar's catalyst H H

H2, 1%Pt on C

Dissolved Lithium in NH3

trans Alkenes

trans more stable

H NH2

C=CCH3

CH3

HLiCH3

H

C=CCH3

H

H

H N

CH3C=CCH3

LiHCH3

H CH3

C=C-78oC

Li in NH3(l)CCH3CH3C

.. .

.

Addition of HX

CH3CH2C CHHBr

CH2CH3CH2C

BrHBr

CH3CH2CCH3

Br

Br

CH3CH2C=CH2

vinyl carbocationsp hybridized

Br2 Addition

C CH Br2C C

HBr

Br

C

Br

Br

C

Br

Br

H

Br2

Oxymercuration HydrationMarkovnikov

CH3CH2C CHHgSO4, H2SO4

H2OCH3CH2C=CH2

OH

an enol

CH3CH2CCH3

O

a ketone

Enol – Keto TautomerizationIntermolecular

3

OH

CH

HCH3CH2C

OH

CH

HCH3CH2C

OH

CH

HCH3CH2C

CH3CH2CCH3

O

Oxymercuration Mechanism

enol

SO42-SO42-

H3O+

tautomerization

OH

CH

HCH3CH2C

H2O

CH3CH2C CHg

HOH

O

CH3CH2CCH3

H2OO

HH

CHg

HCH3CH2C

vinyl carbocation

Hg+2

CH3CH2C CHg

H

HgSO4, H2SO4(aq)CHCH3CH2C

Hydroboration HydrationAnti-Markovnikov

2) H2O2, NaOH

1) disiamyl borane

O

CH3CH2CH2CH

CHCH3CH2C

an enol

OH

CH3CH2CH=CH2

an aldehyde(sia)2BH

B

H

Hydroboration Mechanism

CH3CH2C CH CH3CH2CH2CH

O1) disiamyl borane

2) H2O2, NaOH

B

H

(sia)2BH

CH3CH2C

H

CH

B(sia)2H2O2, NaOH

CH3CH2CH=CH2

OH

enol

tautomerization

Draw the Products

C CH1) disiamylborane, THF

2) H2O2, NaOH

HgSO4, H2SO4 (aq)

C CH1) disiamylborane, THF

2) H2O2, NaOH

HgSO4, H2SO4 (aq)

CH2CH

CCH3

O

O

Ozonolysis

CH3CH2C CCH3O3

H2O CH3CH2C=O

OH

O=CCH3

OH

+

2 carboxylic acids

Acidity of Terminal Alkynes

Acetylide Formation

Alkylation of Acetylide IonsHomologations using SN2 rxn

CH3CH2CH2C C HNaNH2

in NH3(l)-78 C

o

CH3CH2CH2C C Na

CBr

H

HH

CH3CH2CH2C CCH3

SN2NH2

Multi-step Syntheses

HC CH Br?

Retrosynthetic AnalysisBegin with the Product

HC CH Br?

Fill in the Reagents

HC CH Br?

1) NaNH2, NH3

2) Br

H2, Lindlar's cat.

HBrROOR, h

How Many Steps?

CHHCCH2CH(CH3)2

H

H

CH3

?

5 Steps

CHHCCH2CH(CH3)2

H

H

CH3

1) NaNH2, NH3

2) CH3I

3) NaNH2, NH3

4) (CH3)2CHCH2Br5) Li, NH3

An unknown compound (A) has a formula of C11H14. Treatment of A with H2/Pd-carbon gives B

(C11H20). Treatment of A with H2 on a Lindlar

catalyst gives C (C11H16). Ozonolysis of C followed

by workup with Zn, HOAc affords formaldehyde and the tricarbonyl compound shown below.

O

+ HCHCH

O

O

O

H

Schematic of the Problem

2) Zn, HOAc

1) O3

H2 / Lindlar's cat.

C11H20C11H14

BH2 / Pd on carbon

A

CC11H16

CH

O

O

O

H

+ HCH

OC

• An initial approach to this problem is to determine the number of degrees of unsaturation in each of the molecules A, B, and C.

• When A (C11H14, 5o unsat.) is hydrogrenated, B (C11H20, 2

o unsat.) is formed. That means that 3 bonds reacted (3 mol. equivalents) to form B.

• When A is treated with H2 over a Lindlar (poisoned) catalyst, 1 mol equiv. of H2 reacts. Since this reaction is specific for the reduction of alkynes to alkenes, 2 of the 3 bonds in A are in the form of a triple bond. The remaining bond must be an alkene.

• We have accounted for three of the five degrees of unsaturation in A, therefore the other two must be rings since they do not react with H2.

Propose Structures for A, B, and C

H2, Pd/C

A B

H2

Lindlar's cat.

1) O3

2) Zn, HOAc(aq)

OO O

H

CO

CH2

Nucleophilic addition to Carbonyl Compounds

C

O

CH3CH3

CH3CH2C C

C

O

CH3CH3

CCH3CH2C

CH3CH2C C

CH3 CH3

OH

C

H3O+

H

Synthesis Problem

C CH

H

CH3CH2

CHCH2CH3

OH

target molecule

from acetylene and any

2- or 3-carbon reagents

Retrosynthetic Analysisfrom acetylene

C CH

H

CH3CH2

CHCH2CH3

OH

target moleculeCH3CH2X

HC CHHCCH2CH3

O