Preparation of Tri- and Tetrasubstituted Allenes via Regioselective Lateral Metalation of Benzylic (Trimethylsilyl)alkynes Using TMPZnCl·LiCl
摘要:
The zincation of various 1-(trimethylsilyl)-3-aryl-1-propynes with TMPZnCl center dot LiCl followed by a Pd-catalyzed coupling with aryl halides provides arylated allenes in 5292% yield. Subsequent metalation with TMPZnCl center dot LiCl and cross-coupling with a second different aryl halide provides regioselectively tetrasubstituted allenes in 4270% yield. This sequence can be performed in a one-pot procedure. DFT calculations and NMR studies support the formation of allenylzinc and propargyllithium intermediates starting from 1-(trimethylsilyl)-3-phenyl-1-propyne.