20

Coupling of diazonium salts

must be strongly electron donating (electron “rich” arenes)

2.8.3.Strategic use in synthesis
1st example

2nd example

2.9Formylation Reactions

The electrophilic species

3.

Aromatic Heterocycles

3.1.

Five Membered Rings

•
•
•
•
•

aromatic
6π electrons
resonance stabilisation 22-28 kcal/mol (benzene 36 kcal/mol)
undergo electrophilic substitution; very reactive
similar reactivity to phenols and anilines

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N

R

NX
2

R

OH (NH2or NR2)

N

OH

+

weakly

alkaline

"azo dye"
strongly coloured

(NH2or NR2)

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NCl
2

R

NO2

NO2

Br

NH2

Br

OH

Br

H2SO4/ H2O

Br2/ FeBr3

Sn / HCl

NaNO2/ HCl

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NO2

NO2

Br

NO2

Br

NH2

Br

NH2

Br

N2

NO2

Br

Br

Br

NO2

Br

Br

Br

Br2

NaNO2/ H2SO4

HSO4

CuBr

reduce

diazotise

reduce

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+

NMe2

S

N

H

O

1. POCl3

2. H2O, CH3CO2Na

S

H

O

74%

+

1. POCl3

2. H2O, CH3CO2Na

82%

N

H

O

NMe2

H

O

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