Reaction of Furan and Thiophene
Reaction of Furan and Thiophene
Reaction of Furan and Thiophene
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Second Electrophilic Substitution in <strong>Furan</strong> <strong>and</strong><br />
<strong>Thiophene</strong><br />
a) Monosubstituted furan & thiophene with electron withdrawing groups such as<br />
COOH, CHO, CN, COR, SO 3 H are less reactive than unsubstitutted compounds<br />
i) EWG at position 2<br />
O 2 N<br />
HNO 3 (incoming E + is directed to m-position i.e. position 4)<br />
S CN S CN<br />
Less reactive than thiopene<br />
O 2 N<br />
+<br />
CH COONO 3 2<br />
O CHO<br />
O 2 N O CHO O CHO<br />
Pyridine<br />
Less reactive than furan<br />
O<br />
COOH<br />
Br 2 / Dioxane<br />
ii) EWG at position 3<br />
3 : 1<br />
(incoming E + is directed to position 5 mainly <strong>and</strong> to position 4<br />
as well )<br />
Br<br />
+<br />
Br O COOH<br />
O COOH<br />
X<br />
EWG<br />
E +<br />
E<br />
X<br />
EWG<br />
(incoming E + is directed to position 5)<br />
Heterocyclic Chemistry
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