Table 2.

Scope of Directing-Group Effects in Ti-Catalyzed [2+2+1] Pyrrole Synthesis

^aCondition A: A mixture of 0.5 mmol 1 (1.1 equiv), 0.5 mmol 2 (1.1 equiv), 0.225 mmol PhNNPh (0.5 equiv) and 0.05 mmol THF₃I₂Ti(NPh) (0.1 equiv) in 2.5 mL CF₃Ph was heated for 2 h. Reactions were quenched with 2 M HCl in MeOH;

^bCondition B: A mixture of 1.0 mmol 1 (2.2 equiv), 0.5 mmol 2 (1.1 equiv), 0.225 mmol PhNNPh (0.5 equiv) and 0.025 mmol [py₂Cl₂TiNPh]₂ (0.05 equiv) in 2.5 mL CF₃Ph was heated for 3 h. Reactions were quenched with 2 M HCl in MeOH;

^c1Isolated and/or NMR yield of major regioisomer drawn and are reported with respect to 2a.

^dReaction run at 80 °C;

^eReaction run at 115 °C.