Solvent Free and Regioselective Hydroboration of Terminal Double Bond for Synthesis of Z-11-Hexadecenol

Abstract

Z-11-Hexadecenol was synthesized in high yield by Wittig and hydroboration reactions without solvent. Initially 1,11-hexadecadiene was synthesized as a result of Wittig reaction between n-pentyl bromide and C -11 aldehyde. Later hydroboration of the diene formed was carried out by in situ generation of borane using sodium borohydride and boron trifluride etherate. The significance of the process lies on the fact that it is solvent free as well as regioselective and the borane:diene ratio was taken as 1:6. The trialkyl borane formed as the result of the above reaction was filtered and the excess diene was recovered. Further oxidation of trialkyl borane resulted in the formation of Z-11-hexadecenol of > 95 % purity. The excess diene recovered from hydroboration reaction showed more purity than its precursor and can be reused again. Thus this method was found to give more atom economy and the process can be scaled up easily without affecting the isomeric purity.