• This reaction is via an E1 reaction step.
• The first step is a keto-enol tautomerism.
• Firstly the aldol is formed, then reaction proceeds to show the formation of the dehydrated product.
• This reaction is harder to control than its base catalysed counterpart - thus the reaction is more unpredictable.
• A crossed aldol reaction can occur if one component is more reactive and cannot form an enol/enolate.
• This reaction can occur in an intramolecular fashion as well as an intermolecular one.


References:

• White J.D.; Blakemore P.R.; Green N.J.; et al., J. Org. Chem., 2002, Volume 67, No. 22, 7750-7760
• Wei H.-X.; Hu J.; Purkiss D.W.; Paré P.W.; Tetrahedron Lett., 2003, Volume 44, Issue 5, 949