Microwave-Assisted Synthesis of Spirofused Heterocycles Using Decatungstodivanadogermanic Heteropoly Acid as a Novel and Reusable Heterogeneous Catalyst under Solvent-Free Conditions

Table 3

H₆GeW₁₀V₂O₄₀·22H₂O catalyzed reaction of cyclohexanone, aldehyde, and urea.

Entry	R	Products^a	Yield^b (%)	M.P (°C)
1	C6H5	2a	87	327–329
2	4-(NO2)C6H4	2b	79	341–343
3	4-(CH3)C6H4	2c	83	348–351
4	2-(Cl)–C6H4	2d	82	321–323

 ^aReaction conditions: cyclohexanone (1.0 mmol), aldehyde (2.0 mmol), urea (3.0 mmol), and decatungstodivanadogermanic acid (3 mmol) irradiated at 80°C under solvent-free condition.