Convergent Domino Knoevenagel Hetero-DielsAlder and Domino Oxidation Hetero-DielsAlder Reactions Encountered in an Unexpected Formation of Novel 5-Aryl-1H-pyrano[2,3-d]pyrimidine-2,4(3H,5H)-diones and 5-Aryl-2,3-dihydro-2-thioxo-1H-pyrano[2,3-d]pyrimidin-4(5H)-ones