To a solution of 2-(2-ethyl-4-formylphenylimino)-1-cyclopentyl-3-thia-1-azaspiro[4.4]nonane (Method D11a; 0.037 g, 0.104 mmol) in EtOH (10 mL) was added malononitrile (0.007 g, 0.104 mmol) and piperidine (4 drops). The reaction mixture was stirred at room temp. for 2 h, then concentrated under reduced pressure. The residue was purified by preparative TLC (20% EtOAc/hex) to give 2-(2-ethyl-4-(2,2-dicyanovinyl)phenylimino)-1-cyclopentyl-3-thia-1-azaspiro[4.4]nonane as a yellow solid (0.012 g, 28%): mp 135-136° C.
