Efficient Synthesis of (P-Chirogenic) o-Boronated Phosphines from sec-Phosphine Boranes

An efficient synthesis of boronated phosphines with an o-phenylene-bridge prepared from sec-phosphine boranes and using benzyne chemistry is reported. Successive reactions of sec-phosphine boranes with n-BuLi and 1,2-dibromobenzene, and then with boron reagents, afford the o-boronatophenylphosphine derivatives in 71% yields. The use of P-chirogenic sec-phosphine boranes leads to the free boronated phosphines with retention of configuration at the P-center after decomplexation. The reaction of P-chirogenic o-boronatophenylphosphine with KHF2 affords the corresponding trifluoroborated phosphine with ee >98%.