Efficient non-catalytic synthesis of substituted 2,3,4,9-tetrahydro-1H-xanthen-1-ones from salicylaldehydes and dimedone

Thermally induced non-catalytic assembling of salicylaldehydes and dimedone in water or ethanol affords 9-(2-hydroxy-4,4-dimethyl-6-oxo-1-cyclohexen-1-yl)-3,3-dimethyl-2,3,4,9-tetrahydro-1H-xanthen-1-ones in 85–95% yields as a sequence of Knoevenagel and Michael reactions.