Hydroboration Kinetics. 10. Kinetics, Mechanism, and Selectivity for Hydroboration of Representative Alkenes with Borinane

Article abstract of DOI:10.1021/ja00325a010

The kinetics of hydroboration of representative alkenes with borinane dimer have been studied at 0 deg C in n-heptane.With many alkenes the reaction shows three-halves-order rate behavior, indicating a fast dissociation of the borinane dimer, followed by the rate-limiting step involving the monomer and the alkene.With a few alkenes the reaction was too fast for accurate rate measurements.The rate data indicate a possible generalization of the earlier conclusions for the mechanism of hydroboration of alkenes by 9-borabicyclo<3.3.1>nonane dimer, (9-BBN)2.The relative rates calculated from the rate constants agree well with those determined competitively.A comparison of the reactivity of borinane toward various classes of alkenes with those of other hydroborating agents, such as 9-BBN, disiamylborane, dibromoborane-methyl sulfide, and thexylchloroborane-methyl sulfide, shows that borinane is similar to 9-BBN in its selectivity and differs markedly from that of disiamylborane, dibromoborane-methyl sulfide, and thexylchloroborane-methyl sulfide.