Reaction of Boranephosphonate Diesters with Pyridines or Tertiary Amines in the Presence of Iodine: Synthetic and Mechanistic Studies
[ 1 ] Instytut Chemii Bioorganicznej Polskiej Akademii Nauk, Polska Akademia Nauk | [ P ] pracownik
2020
artykuł naukowy
angielski
EN Boranephosphonate diesters react with heteroar-omatic and certain tertiary amines in the presence of an oxidant (I-2) to afford the boron-modified phosphodiester analogues containing a P-B-N structural motif. Our multinuclear P-31 and B-11 NMR spectroscopy studies lend support for a two-step mechanism involving generation of a lambda(3)-boranephosphonate ntermediate that immediately coordinates an amine in the solvent cage, leading to B-pyridinium or B-ammonium boranephosphonate betaine derivatives. We found that the type of the solvent used (e.g., dichloromethane vs acetonitrile) significantly affected the course of the reaction, resulting in either formation of boron-modified derivatives or loss of the boron group with a subsequent oxidation of the phosphorus atom. In aprotic, electron-donating, polar solvents., e.g., acetonitrile (ACN) and tetrahydrofuran (THF), a lambda(3)-boranephosphonate intermediate can also coordinate solvent molecules forming P-B-ACN or P-B-THF complexes that may influence the type of the products formed.
4312 - 4323
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