Figure 2. Scope of Rh-catalysed coupling of aryl hydrazines with allene.
[a]Isolated yield. [b]Determined by chiral HPLC. [c]ee after recrystallization from tosylic acid salt. [d]Reaction in 1.0 mmol scale. [e][Rh(cod)Cl]2 (2 mol%), L1 or L2 (8.0 mol%). [f]Reaction at 100 °C. [g]The NMR spectrum of 1j is not fully pure due to contamination of acetone (formation of hydrazone) during the purification. This problem can be avoided in the process of one-pot asymmetric synthesis of N-allylic indoles. Chp, cycloheptyl; HPLC, high-performance liquid chromatography; Phth, phaloyl; TBS, tert-butylsilyl.