Process for preparing bisallylboranes and nonaromatic boronic acids

A process for preparing boronic acid esters by reaction of a diene with sodium borohydride in the presence of a first oxidant selected from the group consisting of an alkyl halide, a dialkyl sulfate, and mixtures thereof to form the corresponding bis(allyl)borane of the formula (I):

• wherein R1-R6 are H, aryl or substituted or unsubstituted C1-C4-alkyl or two of the radicals R1-R6 may be closed to form a cyclic system,
• and further reaction of the borane (I) with an alkene (II) or alkyne (IV) to:
• give the
• alkylbis(allyl)borane (III) or alkenylbis(allyl)borane (V):
• wherein the radicals R7 to R12 are:
• aryl, substituted or unsubstituted, alkyl-(C1-C8), which may be branched and/or substituted, alkoxy-(C1-C8), acyloxy-C1-C8), O-phenyl, fluorine, chlorine, NO2, NH2, NHalkyl-(C1-C8), Nalkyl2-C1-C8), CN, CHO, SO3H, SO3R, SO2NH2, SO2N(alkyl-(C1-C8))2, SO2-alkyl-(C1-C8), COO-alkyl-(C1-C8), CONH2, CO-alkyl-(C1-C8), NHCHO, CF3, 5-membered heteroaryl or 6-membered heteroaryl, where two or radicals R7 to R12 may also form a cyclic ring system which may contain heteroatoms and directly oxidizing the alkylbis(allyl)borane (III) or alkenylbis(allyl)borane (V) In the presence of a second oxidant to form the corresponding bisallyl alkylboronate or alkenylboronate.