Question

Draw the product of each of the following sigmatropic rearrangements:

Short answer

Sigmatropic reactions fall under the category of pericyclic reactions. In the transition state of a sigmatropic rearrangement, the group that drifts is partially connected to the migratory origin and the migration terminus.

Step-by-step solution

Sigmatropic rearrangement

Sigmatropic reactions fall under the category of pericyclic reactions. In the transition state of a sigmatropic rearrangement, the group that drifts is partially connected to the migratory origin and the migration terminus.

Drawing the product of each of the sigmatropic rearrangement reactions

a. The given compound undergoes a [3,3] sigmatropic rearrangement to form 6-(but-3-en-2-yl) cyclohexa-2,4-dienone. It further undergoes tautomerization to form 2-(but-3-en-2-yl)phenol. The reaction is shown below.

Reaction (a)

b. The given compound undergoes a [3,3] sigmatropic rearrangement to form (E)-6-(but-2-en-1-yl)cyclohexa-2,4-dienone. It further undergoes tautomerization to form (E)-2-(but-2-en-1-yl)phenol.

The reaction is shown below.

Reaction (b)

c. The given compound undergoes a [5,5] sigmatropic rearrangement to form (E)-4-methyl-4-(penta-2,4-dien-1-yl)cyclohexa-2,5-dienone. It further undergoes tautomerization to form (E)-4-(penta-2,4-dien-1-yl)phenol.

The reaction is shown below.

Reaction (c)

d. The given compound undergoes a [5,5] sigmatropic rearrangement to form (E)-4-(penta-2,4-dien-1-yl)cyclohexa-2,5-dienone. It further undergoes tautomerization to form 4-((2E,4E)-hexa-2,4-dien-1-yl)phenol.

The reaction is shown below.

Reaction (d)