Synthesis, Structure, and Thermolysis of a Pentacoordinate 1,2-Oxastibetane

Isomeric pentacoordinate 1,2-oxastibetanes bearing the Martin ligand have been synthesized by the reactions of bromo(2-hydroxyalkyl)stiboranes with sodium hydride of which one of the isomers was characterized by X-ray crystallographic analysis and NMR spectroscopy. Thermolysis of the isomer shown (CD₃CN, 140 °C) afforded the oxirane with retention of configuration, while its thermolyses in the presence of lithium bromide and LiBPh₄·3DME provided the oxirane with inversion of configuration and the olefin. The addition of the salts in the thermolyses of this pentacoordinate 1,2-oxastibetane controls both the stereochemistry of the oxirane formed and the ratios of the three main products.