Steric Hindrance-Controlled Pd(0)-Catalyzed Coupling-Cyclization of 2,3-Allenamides and Organic Iodides. An Efficient Synthesis of Iminolactones and γ-Hydroxy-γ-lactams.

Under the catalysis of 1 mol % Pd(PPh[sub 3])[sub 4], the reaction of 4,4-disubstituted 2,3-allenamides and organic iodides in toluene afforded iminolactones stereospecifically in >90% yields using K[sub 2]CO[sub 3] (2 equiv) 5 mol % TBAB as the base. A similar reaction with 4-monosubstituted 2,3-allenamides afforded γ-hydroxy-γ-lactams in relatively lower yields. The N/O-attack selectivity may be determined by the steric effect at the 4-position of 2,3-allenamides. [ABSTRACT FROM AUTHOR]