Q30E - Organic Chemistry (Mcmurry)

Question

Vinyl-substituted cyclopropanes undergo thermal rearrangement to yield cyclopentenes. Propose a mechanism for the reaction, and identify the pericyclic process involved.

Step-by-Step Solution

Answer

The mechanism for the thermal rearrangement to produce cyclopentene can be proposed and identify the involvement of the pericyclic process.

Step 1: Sigma tropic rearrangement

The reaction is [1,3] sigma tropic rearrangement. There is an involvement of 2 electron pairs in the reaction. Thus, it is under thermal conditions through antarafacial pathway

Step 2: Cyclic mechanism for the transformation

The cyclic mechanism for the thermal rearrangement of vinyl substituted cyclopropanes into cyclopentenes can be drawn as,

The pericyclic process is involved in the shift of 1,3-sigmotropic shift.