Scheme 2. Structures of Polyheterocycles^,,,

The isocyanide, aldehyde, amine, and carboxylic acid components are depicted in red, green, blue, and black, respectively. The Ugi reaction conditions are as follows: 1 (1.0 mmol), 2 (1.0 mmol), 3 (1.0 mmol), 4 (1.0 mmol), MeOH (1.0 mL), 15 h, and 25 °C.

Reaction conditions: 5 (0.5 mmol), CH₃SO₃H (0.1 mL), CH₃CN (2.0 mL), 25 °C, and 12 h.

Reaction conditions: 5 (0.5 mmol), CH₃SO₃H (1.0 mL), CH₃CN (0.5 mL), 25 °C, 12 h. or HCOOH (2.0 mL), 25 °C, and 4 h.

Reaction conditions: CH₃SO₃H (2.0 mL), 70 °C, and 1 h.