Process for the trans-selective hydroboration of internal alkynes

Process for highly stereoselective trans-hydroboration of internal alkynes comprising the steps of reacting an alkyne of the formula I:

• with a borane of the formula X1X2BH in the presence of a ruthenium catalyst to yield an alkene of the general formula (II):
• wherein:
• R1 and R2 are the same or different and are each be selected from:
• a. straight chain or branched chain aliphatic hydrocarbons, said aliphatic hydrocarbons optionally including heteroatoms and/or aromatic hydrocarbons and/or heteroaromatic hydrocarbons in the chain and/or having one or more substituents selected from C1-C20-alkyl, C5-C8-heterocycloalkyl or C6 to C20 aromatic hydrocarbon, C5 to C20 heteroaromatic hydrocarbon or aryl-(C1-C6)-alkyl, heteroaryl-(C1-C6)-alkyl, or heteroatoms, or
• b. aromatic hydrocarbons having 5 to 20 carbon atoms or heteroaromatic hydrocarbons having 1 to 20 carbon atoms, said aromatic or heteroaromatic hydrocarbons each optionally having one or more substituents selected from C1-C20-alkyl, C5-C8-heterocycloalkyl or C6 to C20 aromatic hydrocarbon, C5 to C20 heteroaromatic hydrocarbon or aryl-(C1-C6)-alkyl, heteroaryl-(C1-C6)-alkyl, heteroatoms, or
• R1 and R2 together form an aliphatic hydrocarbon chain having 4 to 30 carbon atoms, optionally including heteroatoms and/or aromatic hydrocarbons in the chain and/or optionally having one or more substituents selected from C1-C20-alkyl, C5-C8-heterocycloalkyl or C6 to C20 aromatic hydrocarbon, C5 to C20 heteroaromatic hydrocarbon or aryl-(C1-C6)-alkyl, heteroaryl-(C1-C6)-alkyl, said aliphatic hydrocarbon chain optionally being substituted by one or more substituents selected from heterosubstituents, straight chain, branched chain, cyclic aliphatic C1 to C20 hydrocarbons, C6 to C20 aromatic hydrocarbon, C5 to C20 heteroaromatic hydrocarbon, aryl-(C1-C6)-alkyl, or heteroaryl-(C1-C6)-alkyl or heteroatoms;
• wherein the borane of the formula X1X2BH is selected from the group of dialkyl boranes or di(alkoxy)boranes wherein X1 and X2 are the same or different and are each selected from straight chain, branched chain or cyclic aliphatic hydrocarbons, or X1 and X2 together form an aliphatic hydrocarbon chain having 2 to 20 carbon atoms, said aliphatic hydrocarbon—group or chain—optionally bound to the boron via an —O-bridge and optionally including heteroatoms in the chain and/or optionally having one or more substituents selected from C1-C20-alkyl, C5-C8-heterocycloalkyl or C6 to C20 aromatic hydrocarbon, C1 to C20 heteroaromatic hydrocarbon or aryl-(C1-C6)-alkyl, heteroaryl-(C1-C6)-alkyl, having identical or different alkyl groups with 2 to 12 carbon atoms or heteroatoms;
• and
• wherein the catalyst used in the inventive process is a cyclyopentadienyl-coordinated ruthenium complex containing the following substructure:
• wherein Rcp1 to Rcp5 are the same or different and are each selected from hydrogen or from straight chain, branched chain or cyclic aliphatic hydrocarbons, optionally including heteroatoms and/or aromatic hydrocarbons in the chain and/or optionally having one or more substituents selected from C1-C20-alkyl, heterocycloalkyl, C5 to C20 aromatic hydrocarbon, C5 to C20 heteroaromatic hydrocarbon or aryl-(C1-C6)-alkyl, heteroaryl-(C1-C6)-alkyl or heteroatoms and wherein further ligands L are coordinated to the central atom ruthenium.