A practical synthesis of novel α-dibromoalkyl- and trimethylsilylmethyl-aminoboranes and derivatives

Addition of LDA to a mixture of trimethylborate and dibromomethane in THF at a temperature of −78 °C leads to the formation of dibromomethyllithium and its capture by borate ester. ClB(OMe)2 converts the resulting borate salt to dimethoxy(dibromomethyl)borane 2. N,N-Dimethylamino(methoxy)(dibromomethyl)borane 3 and N,N-bis(dimethylamino)(dibromomethyl)borane 4 were prepared by an amination reaction between N,N-dimethylaminotrimethylsilane and dimethoxy(dibromomethyl)borane 2. To obtain dichlorotrimethylsilylmethylborane 7 not containing the α-halomethyl group, N,N-bis(dimethylamino)(trimethylsilylmethyl)borane 5 was first obtained from the reaction of ClB(NMe2)2 with an organolithium reagent. Dimethoxy(trimethylsilylmethyl)borane 6 was then prepared by methoxylation of compound 5. Finally, compound 7 was prepared by chlorination of 6 using BCl3. The chemical structures of these compounds were determined using 13C, 1H, 11B NMR and GC/MS/MS techniques.

Research highlights▶ In this study we have reported the synthesis of six novel boran compounds which are important in the boron chemistry. ▶ Of these, in particularly, Dibromomethylbisdimethylaminoborane is significant borelectrophiles in that it contains both a halogen and an amine group, and is a convenient reagent for the preparation of novel iminium salts containing a B atom. ▶ The chemical structures of these compounds were characterized by using spectroscopic methods, 13C, 1H, 11B NMR and GC/MS/MS techniques.