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

GRAPHICAL ABSTRACT

ABSTRACT

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 LiBH₄ to 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.

KEYWORDS:

• Borane complex
• phospholene oxide
• phosphonium salt
• alkoxy-phosphonium salt
• dynamic resolution

Acknowledgments

The publication of the work reported herein has been supported by NTP-HHTDK-15-0052. The publication of the work reported herein has been supported by ETDB at BME.

Funding

The authors acknowledge the Hungarian Research Fund for financial support (Grant No. PD116096).