Below are shown the mechanistic steps involved in the Aldol reaction of a symmetrical cyclic ketone. The final enone is formed in a good yield both in acid or base conditions. Here the acid-catalysed reaction is used to illustrate the mechanism.
‘Click’ the different stages to view 3D models of the reaction:
D. S. Noyce and W. A. Pryor, J. Am. Chem. Soc., 1955, 77, 1397–1401.
C. L. Perrin and K.-L. Chang, J. Org. Chem., 2016, 81, 5631–5635.