The mechanism of Robinson annelation (also known as Robinson annulation) involves the sequential process of a Michael addition-aldol reaction leading to a new six-membered ring. The formation of a stable enolate occurs first as shown below, here of a 1,3-diketone:
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Below are shown the three stages of the Robinson annelation mechanism. ‘Click’ the different stages to view 3D models of the reaction:
Step 1: Conjugate addition
Step 2: Intramolecular aldol reaction
Step 3: E1cb dehydration