Phosphine-Boranes Based on the 7-Phosphanorbornene Framework: a Regioselective Approach to the Monoboranes of the Dimers of Phospholes

The reaction of dimers of phosphole oxides (3a–e) with an excess of dimethylsulfide borane follows an unexpected route to give phosphine-boranes 5a–e based on the 7-phosphanorbornene framework in a regioselective manner and in good yields. In small quantities, the diboranes (10a–e), that can be synthesized in acceptable yields by the reaction of the corresponding diphosphines 12a–e with borane, were also formed.