Convenient method for the preparation of catecholborane and promotion of the formation of alkenyl catecholborane using BH3 complexes

Article abstract of DOI:10.1016/0022-328X(93)80135-X

Catecholborane is prepared in benzene by passing B2H6, generated from I2/NaBH4, through a suspension of catechol at 25 deg C.The reagent prepared in this way is used for hydroboration-oxidation of representative alkenes and alkynes at 80 deg C.Hydroboration of 1-alkynes followed by iodination with I2/NaOH gives the corresponding trans-1-alkenyl iodides in 70-72percent yield.The alkenyl catecholboranes can be prepared at 25 deg C by performing the reaction in the presence of 10 molepercent of H3B:N(C2H5)2Ph or H3B:THF.The reaction is believed to go through hydroboration of thealkynes by borane followed by exchange with catecholborane.Studies of the preparation of dialkylphenoxyboranes and alkenyldiphenoxyboranes through hydroboration of 1-decene and 1-decyne by use of H3B:N(C2H5)2Ph and phenol are also reported.