Tritium and deuterium labelling studies of alkali metal borohydrides and their application to simple reductions

Article abstract of DOI:10.1002/(SICI)1099-1344(199608)38:8<693::AID-JLCR883>3.0.CO;2-4

Simple and facile syntheses of highly deuterated and tritiated LiBH₄, NaBH₄ and KBH₄ were achieved by hydrogen Isotope exchange with deuterium or tritium gas at elevated temperatures. The exchange products were characterized by boron, proton and deuterium or tritium NMR spectroscopy. The extent of isotope (²H or ³H) incorporation was calculated from the patterns of ¹¹B NMR spectra. Several samples of tritiated NaBH₄ were treated with BF₃-Et₂O to produce tritiated borane-THF complex, which is an electrophilic reducing agent. The utility of both the borohydride reagents and borane-THF complex in labelling reactions was confirmed by exemplary reductions leading to specifically labelled products. The extent and orientation of labelling in the reduction products was assessed by a combination of radio-HPLC analysis, ¹H, ²H or ³H NMR and mass spectrometry.