Scheme 5. Various Isocyanides in the Synthesis of Polycyclic Quinazolinones via Radical Cyclization^–

Acid, aldehyde, isocyanide, and cyanamide components are depicted with red, blue, green, and pink color, respectively.

Ugi reaction was carried out using 36 (1 mmol), 37 (1 mmol), 8 (1 mmol), and 38 (1 mmol) in TFE (1 M) for 12 h at r.t.

Radical cyclization conditions: 39–41a (0.15 mmol), tributyltin hydride (0.3 mmol), AIBN (0.15 mmol), benzene (7 mL), reflux, overnight.

Yield refers to purified products.