DDQ (2 3-dichloro-5 6-dicyano-1 4-benzoquinone) is highly electron-deficient and readily performs dehydrogenation and cyclization. Also used to bring aromaticity in natural products and insertion of the carbonyl group.

The substrate must have allylic and benzylic hydrogens to perform dehydrogenation by DDQ. One equivalent DDQ produces one double bond.

Different important applications of DDQ are as follows:

  • DEHYDROGENATION
  • DEHYDROGENATION CYCLIZATION
  • INSERTION OF OXYGEN

DDQ: Dehydrogenation

Aromatisation can be easily achieved through dehydrogenation using DDQ if the ring already had double bond or fused with benzene ring.

Mechanism:

  • STEP 1: Hydride abstraction from the benzylic position by DDQ
  • STEP 2: proton abstraction by phenolate ion

1,2 shift of a methyl group to bring aromitisation to ring if substituents are blocking dehydration by DDQ

Mechanism:

DDQ: Dehydrogenation and Cyclization

Problem 1

Mechanism:

Problem 2

Mechanism:

DDQ: Insertion of Oxygen

Insertion of carbonyl group at allylic or benzylic position where dehydration is not possible.

Mechanism:

Also read

3 thoughts on “DDQ: Dehydrogenation and Cyclization

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