Method for synthesizing cyclohexyl-substituted phosphines

A process for preparing compounds of formula I

• in which
• R is a radical of formula II
• or a linear or branched alkyl radical which has from 1 to 8 carbon atoms and bears 1, 2, 3 or 4 radicals of formula III
• and may also bear from 1 to 4 substituents of formula IV
• X—(CH2)ab—YR7 (IV)
• X and Y are each independently O or NR8;
• each R1 is independently C1-C4-alkyl, C1-C4-haloalkyl, C1-C4-hydroxyalkyl, C3-C10-cycloalkyl, C3-C10-halocycloalkyl, halogen, OR2 or COR3;
• R2 is H or C1-C4-alkyl;
• R3 is H, OR4 or NR5R6;
• R4, R5 and R6 are each independently H or C1-C4-alkyl;
• R7 is H, C1-C4-alkyl or C2-C4-hydroxyalkyl;
• or, in the case that two substituents of formula IV are bonded to the same carbon atom or to two adjacent carbon atoms of the alkyl radical, two R7 radicals may also together form a linear or branched alkylene group having from 1 to 6 carbon atoms;
• R8 is H, C1-C4-alkyl or C2-C4-hydroxyalkyl;
• each x is independently 0 or an integer from 1 to 3;
• a is 2, 3 or 4;
• b is 0 or an integer from 1 to 10;
• and
• # denotes the point of attachment to the rest of the molecule;
• or hydrohalides thereof, comprising the following:
• reacting compounds of formula V
• in which
• R′ is a radical of formula II or a linear or branched alkyl radical which has from 1 to 8 carbon atoms and bears 1, 2, 3 or 4 radicals of formula VI
• and may also bear from 1 to 4 substituents of formula IV;
• and
• Z is halogen;
• with hydrogen at a pressure of from 10 to 300 bar.