Preparation of P-heterocyclic phosphine boranes and optically active phosphine oxides via phosphonium salts.

The preparation of 3-phospholene boranes and optically active 3-phospholene oxides was elaborated via the corresponding cyclic chloro-phosphonium salt intermediates. The 3-phospholene oxides were reacted with oxalyl chloride to afford the corresponding chloro-phosphonium salts, which were reacted with LiBH4to afford 3-phospholene boranes. This procedure is a practical one-pot method for the deoxygenation and borane complex formation of 3-phospholene oxides without using silanes. It was shown that 3-chlorophospholenium salts can be reacted with chiral alcohols to give diastereomerically enriched cyclic alkoxy-phospholium salt intermediates, which were converted to enantiomerically enriched 3-phospholene oxides by Arbuzov collapse. [ABSTRACT FROM PUBLISHER]