Ninhydrin reacted expeditiously with thirteen active methylene compounds on montmorillonite K10 clay at room temperature to furnish, in 5 min, a Knoevenagel condensate in one case, aldols in six cases, aldol-derived cyclic hemiketals in three cases, and interesting products in the remaining three cases. Almost identical results were obtained, but faster, when the reactions were carried out in water on steam-bath. The structures of two novel products were also confirmed by single-crystal X-ray diffraction analysis.
Kundu, Sandip Kumar; Patra, Amarendra; Pramanik, Animesh, Indian Journal of Chemistry - Section B Organic and Medicinal Chemistry, 2004, vol. 43, # 3, p. 604 - 611
A convenient and efficient methodology for the synthesis of densely substituted pyrrole-fused isocoumarins, which employs solid-supported silicasulfuricacid (SSA) as catalyst, has been developed. When the mixture of ninhydrin adducts of acetylacetone/ethyl acetoacetate and primary amines was heated on the solid surface of SSA undersolvent-freeconditions, the pyrrole-fused isocoumarins were formed