Insights into the Conversion of Propargylic Tosylates into Bromoallenes.

All aspects of the title reaction, essentially the only entry into optically active 3-monosubstituted-1-bromoallenes up to now, have been probed systematically for the first time. The new results show that: (1) there is no need to purify CuBr or to exclude air or moisture, (2) addition of Cu(II) led to even higher enantiopurity, and (3) Et2O is the best solvent. Much better selectivities were obtained under the new conditions. [ABSTRACT FROM AUTHOR]