Table 2. Substrate Scope for Imidazo[1,5-a]pyridines and Aldehydes^a.

^aIsolated yields, reaction conditions A (3a–3k): 1 (0.28–0.52 mmol, 1.0 equiv), 2a (12.36 mmol, 1.0 mL), and solvent EtOH (0.5 mL, if required), reaction conditions B (3l): 1 (0.52 mmol, 1.0 equiv) and 2b (9.27 mmol, 1.0 mL), reaction conditions C (3m–3w): 1 (0.47–0.52 mmol, 1.0 equiv), 2 (0.71–0.78 mmol, 1.5 equiv), and solvent EtOH (0.5 mL), reaction conditions D (3x): 1a (0.26 mmol, 1.0 equiv), 4-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one (0.26 mmol, 1 equiv), and 2a (12.36 mmol, 1.0 mL), and reaction conditions E (3y): 1b (0.26 mmol, 1.0 equiv), 1g (0.26 mmol, 1.0 equiv), 2g (0.39 mmol, 1.5 equiv), and solvent EtOH (0.5 mL).