Molecular Addition Compounds. 15. Synthesis, Hydroboration, and Reduction Studies of New, Highly Reactive tert-Butyldialkylamine−Borane Adducts

Two series of tert-butyldialkylamines have been prepared and examined for borane complexation. The complexing ability of each amine in the two series examined decreases in the order shown. First series:  t-BuN(CH2CH2)2O 1a > t-BuNEt2 1b > t-BuNPrn21c > t-BuN(CH2CH2OMe)2 1d ≫ t-BuNBui2 1e. Second series:  t-BuNBuiMe 2a > t-BuNPriMe 2b > t-BuNBuiEt 2c > t-BuNBuiPrn 2d ≫t-BuNPriEt 2e. The reactivity of the corresponding borane adducts toward 1-octene increases in the reverse order. The following amines form highly reactive liquid borane adducts hydroborating 1-octene in tetrahydrofuran at room temperature in less than 1 h:  t-BuN(CH2CH2OMe)2, t-BuNBuiEt, and t-BuNPriMe. The limit of borane complexation among the amines examined is reached for t-BuNBui2 exchanging borane neither with BMS nor with BH3−THF. Among the various borane adducts prepared, the more promising borane adducts, t-Bu(CH3OCH2CH2)2N−BH3 (7), t-BuMePriN−BH3 (8), and t-BuEtBuiN−BH3 (9), were selected for complete hydroboration and reduction st...