The following is an example of a Johnson-Claisen reaction, which is a Claisen reaction variant. Provide the possible mechanism for the first step in the reaction.

Stepwise mechanism of the Claisen rearrangement showing electron movement and intermediates.

Detailed mechanism of the Claisen rearrangement with electron flow and structural changes.

Another representation of the Claisen rearrangement mechanism illustrating electron shifts.

Final step of the Claisen rearrangement mechanism showing product formation and electron movement.