Synthesis of B-trisubstituted borazines via the rhodium-catalyzed hydroboration of alkenes with N,N′,N″-trimethyl or N,N′,N″-triethylborazine

Hydroboration of terminal and internal alkenes with N,N′,N″-trimethyl- and N,N′,N″-triethylborazine was carried out at 50 °C in the presence of a rhodium(I) catalyst. Addition of dppb or DPEphos (1 equiv.) to RhH(CO)(PPh3)3 gave the best catalyst for hydroboration of ethylene at 50 °C, resulting in a quantitative yield of B,B′,B″-triethyl-N,N′,N″-trimethylborazine. On the other hand, a complex prepared from (t-Bu)3P (4 equiv.) and [Rh(coe)2Cl]2 gave the best yield for hydroboration of terminal or internal alkenes.

Graphical abstractA complex prepared from dppb or DPEphos (1 equiv.) to RhH(CO)(PPh3)3 gave the best catalyst for ethylene and (t-Bu)3P (4 equiv.) and [Rh(coe)2Cl]2 was used for terminal or internal alkenes.Figure optionsDownload full-size imageDownload as PowerPoint slide