Cyclizations to 6-Membered Aromatic Heterocycles

Treatment of benzoylisocyanate 1562 with trimethylsilyl ketene 1563 gives the oxazine 1564 which reacts, e.g., with enamines 1565 to give pyridine-2-ones 1567, 

A two-necked reaction flask, equipped with a magnetic stirrer, efficient reflux condenser carrying a calcium chloride valve, and gas inlet tube, is charged with L-lysine 1442f (5 g, 34 mmol), xylene (450 mb), HMDS 2 (50 mb, 240 mmol), and a few drops of MesSiCl 14. The mixture is heated under reflux under a gentle stream of 

Triflic acid (0.032 g) is added through a septum to a stirred mixture of 2,5-hex-andione 1487 (1.95 g, 0.017 mol) and HMDS 2 (7.4 mb, 0.035 mol) whereupon an exothermic reaction results and hexamethyldisiloxane 7 is removed by distillation through a short-path distillation head. When the reaction subsides (15 min) 81% pure 2,5-dimethylpyrrole 1494, b.p. 165 °C, is isolated by distillation [41]. 

Base-catalyzed, Add-catalyzed and Thermal Eliminations of Trimethylsilanol. Peterson Reactions 

---