Process for preparing biaryls in the presence of palladophosphacyclobutane catalysts

A process for preparing biaryls of the formula (1),

• where
• R1 to R10 are identical or different and are each, independently of one another, hydrogen, straight-chain or branched alkyl having from 1 to 8 carbon atoms, cycloalkyl which has from 3 to 7 carbon atoms in the ring and may bear C1-C4-alkyl(s) as substituent(s), C2-C8-alkenyl, C2-C8-alkynyl, fluorine, chlorine, hydroxy, OLi, ONa, OK, OMg0.5, OMgCl, OMgBr, alkoxy having from 1 to 8 carbon atoms, NH2, NHR′, NR′2, NH(C═O)R′, NH(C═O)OR′, NH(C═O)NR′2, NO2, SO2R′, SOR′, POphenyl2, PO—(C1-C8-alkyl)2, PO3—(C1-C8-alkyl)2, C(═O)R′, C(═O)NR′2, C(═O)OR′, CN, CO2Li, CO2Na, CO2K, CO2MgCl, CO2MgBr, phenyl, substituted phenyl, aralkyl or heteroaryl;
• or two adjacent radicals R(n) and R(n+1) correspond to a bridging 1,ω-alkanediyl chain having from 3 to 8 carbon atoms or a bridging ethylene dioxy or methylene dioxy chain;
• or two adjacent radicals R(n) and R(n+1) correspond to a unit of the formula
• and the radicals R′ are, independently of one another, hydrogen, C1-C8-alkyl, C1-C8-alkoxy or phenyl,
• and the ring atoms X1 to X10 are either all carbon atoms or at most one heteroatom is present in each of the two linked rings A and B such that any ring member RiXi is N, or two adjacent ring members R2X2 and R3X3, or R4X4 and R5X5, or R7X7 and R8X8, or R9X9 and R10X10, are replaced by S, O or NR″, where R″ is hydrogen, alkyl having from 1 to 8 carbon atoms, SiR′3 or C(═O)R′,
• by coupling aromatics of the formula (2) with an aromatic boron compound of the formula (3),
• where LG is one of the leaving groups fluorine, chlorine, bromine, iodine, triflate, perfluoro-(C1-C8)alkylsulfonate, mesylate, tosylate, nosylate, brombenzenesulfonate or N(OSO2CF3)2;
• Q1 and Q2 are identical or different and are each OH or a radical of the formula —O—(C1-C8)alkyl, —O—(C2-C8)-alkenyl, —O—(C2-C8)alkynyl, —O-aryl or —O-alkylaryl,
• or Q1, Q2 and the adjacent boron atom form a cyclic boric ester of the alcohols (C3-C12)-cycloalkane-1,2-diol, (C5-C12)-cycloalkene-1,2-diol, (C5-C12)-cycloalkane-1,3-diol, (C5-C12)-cycloalkene-1,3-diol or of alcohols of the formulae (Va) to (Ve),
• where R1b to R8b are identical or different and are each, independently of one another, hydrogen, C1-C12-alkyl, C1-C12-hydroxyalkyl, C2-C12-alkenyl, C2-C12-alkynyl, C3-C12-cycloalkyl, (C1-C12-alkoxy, (C1-C12)-acyloxy, O-phenyl, O-benzyl, aryl, heteroaryl, fluorine, chlorine, bromine, iodine, NO2, NH2, N(alkyl)2, N[Si(C1-C4-alkyl)3]2, CF3, CCl3 or CBr3,
• and/or two adjacent radicals R1b to R8b together form a 5- to 8-membered aliphatic or aromatic ring, and n is an integer from 2 to 12,
• or Q1 and Q2 together form a divalent radical of the formula (Vf)
• wherein the coupling is carried out in the presence of a palladium compound of the formula (IV),
• where R1a and R2a are each, independently of one another hydrogen, (C1-C4)-alkyl, (C3-C12)-cycloalkyl, (C1-C4)-alkoxy, fluorine, N-(C1-C4-alkyl)2, CO2—(C1-C4-alkyl), OCO—(C1-C4)-alkyl or substituted or unsubstituted aryl;
• R3a, R4a, R5a and R6a are, independently of one another, (C1-C8)-alkyl, (C3-C8)-cycloalkyl, substituted or unsubstituted aryl;
• or R1a and R2a, or R2a and R3a, or R3a and R4a, together form an aliphatic ring having from 4 to 10 carbon atoms,
• or R5a and R6a together with the P atom form a saturated or unsaturated 4- to 9-membered ring,
• or R4a and R5a form a bridging 1,ω-alkanediyl chain having from 2 to 7 carbon atoms;
• and
• Y is an anion of an inorganic or organic acid, a α,γ-diketo compound or a 5- or 6-membered nitrogen-containing heterocycle,
• and in the presence of a base and a solvent at temperatures of from 20° C. to 200° C.