Process for preparing biaryls in the presence of...

Details Process for preparing biaryls in the presence of... Process for preparing biaryls in the presence of...

2000-07-13

2002-05-21

Aulakh, Charanjit S. (Department: 1625)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C549S484000, C549S083000, C548S564000, C585S425000, C585S467000, C585S469000, C546S259000, C546S276400, C546S280400, C546S283400

Reexamination Certificate

active

06392047

ABSTRACT:

BACKGROUND OF THE INVENTION
The number of important intermediates in the chemical industry which contain a biaryl structure has increased greatly in recent years. Owing to their applications in the pharmaceutical and agricultural sectors, producers of such intermediates are concerned not only with price, but also with the high purity requirements. For these reasons, highly active, stable and highly selective catalyst systems for the C,C couplings mostly employed for preparing unsymmetrical biaryls are sought. Particularly in the case of couplings of nonactivated aromatics, especially chloroaromatics, the catalyst systems known hitherto generally require the use of large amounts of catalyst (up to 5 mol % or more) in order to achieve industrially useful conversions. Nevertheless, the compositions of the reaction mixtures obtained are often so complex that simple recycling of the catalyst is no longer possible and as a result the high catalysts costs stand in the way of industrial implementation.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to prepare biaryls in high yields, high selectivity and high purity and to use catalyst systems which can be obtained simply and inexpensively and are stable on storage, lead to a high TON (turnover number) and TOF (turnover frequency) and have long operating lives.
It has surprisingly been found that palladaphosphacyclobutanes meet the abovementioned requirements and even in very small amounts make Suzuki couplings, even of chloroaromatics, possible under gentle conditions. The reaction products are obtained in high yields and in high purity even after only simple and inexpensive purification steps. Astonishingly, the palladaphosphacyclobutanes used at the same time have very high activity and high stability so that it is possible to use very small amounts of catalyst. The small amounts of catalyst result in economic and ecological advantages since waste products and waste-intensive work-up processes are avoided. The process of the invention thus meets the demands which are made of a process which can readily be implemented in industry.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a process for preparing biaryls of the formula (1),
where
R
1
to R
10
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 C
1
-C
4
-alkyl(s) as substituent(s), C
2
-C
8
-alkenyl, C
2
-C
8
-alkynyl, fluorine, chlorine, hydroxy, OLi, ONa, OK, OMg
0.5
, OMgCl, OMgBr, alkoxy having from 1 to 8 carbon atoms, NH
2
, NHR′, NR′
2
, NH(C═O)R′, NH(C═O)OR′, NH(C═O)NR′
2
, NO
2
, SO
2
R′, SOR′, POphenyl
2
, PO—(C
1
-C
8
-alkyl)
2
, PO
3
—(C
1
-C
8
-alkyl)
2
, (C═O)R′, C(═O)NR′
2
, C(═O)OR′, CN, CO
2
Li, CO
2
Na, CO
2
K, CO
2
MgCl, CO
2
MgBr, phenyl, substituted phenyl, aralkyl or heteroaryl; or two adjacent radicals R
(n)
and R
(n+1)
correspond to a bridging 1,&ohgr;-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, C
1-C
8
-alkyl, C
1
-C
8
-alkoxy or phenyl, and the ring atoms X
1
to X
10
are either all carbon atoms (biphenyls) or at most one heteroatom is present in each of the two linked rings A and B such that any ring member R
i
X
i
is N (phenylpyridines, bipyridines), or two adjacent ring members R
2
X
2
and R
3
X
3
, or R
4
X
4
and R
5
X
5
, or R
7
X
7
and R
8
X
8
, or R
9
X
9
and R
10
X
10
, are replaced by S, O or NR″ (e.g. phenylthiophenes, phenylpyrroles, phenylfurans, pyridylfurans, pyridylpyrroles), 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-(C
1
-C
8
)alkylsulfonate, mesylate, tosylate, nosylate (p-nitrophenylsulfonate), brombenzenesulfonate or N(OSO
2
CF
3
)
2
;
Q
1
and Q
2
are identical or different and are each OH or a radical of the formula —O—(C
1
-C
8
)alkyl, —O—(C
2
-C
8
)-alkenyl, —O—(C
2
-C
8
)alkynyl, —O-aryl or —O-alkylaryl, or Q
1
, Q
2
and the adjacent boron atom form a cyclic boric ester of the alcohols (C
3
-C
12
)-cycloalkane-1,2-diol, (C
5
-C
12
)-cycloalkene-1,2-diol, (C
5
-C
12
)-cycloalkane-1,3-diol, (C
5
-C
12
)-cycloalkene-1,3-diol or of alcohols of the formulae (Va) to (Ve),
where R
1
b to R
8
b are identical or different and are each, independently of one another, hydrogen, C
1
-C
12
-alkyl, C
1
-C
12
-hydroxyalkyl, C
2
-C
12
-alkenyl, C
2
-C
12
-alkynyl, C
3
-C
12
-cycloalkyl, (C
1
-C
12
)-alkoxy, (C
1
-C
12
)-acyloxy, O-phenyl, O-benzyl, aryl, heteroaryl, fluorine, chlorine, bromine, iodine, NO
2
, NH
2
, N(alkyl)
2
, N[Si(C
1
-C
4
-alkyl)
3
]
2
, CF
3
, CCl
3
or CBr
3
,
and/or two adjacent radicals R
1
b to R
8
b together form a 5- to 8-membered aliphatic or aromatic ring, e.g. a phenyl ring, and n is an integer from 2 to 12,
or Q
1
and Q
2
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 R
1
a and R
2
a are each, independently of one another hydrogen, (C
1
-C
4
)-alkyl, (C
3
-C
12
)-cycloalkyl, (C
1
-C
4
)-alkoxy, fluorine, N(C
1
-C
4
-alkyl)
2
, CO
2
—(C
1
-C
4
-alkyl), OCO—(C
1
-C
4
)-alkyl or substituted or unsubstituted aryl;
 R
3
a, R
4
a, R
5
a and R
6
a are, independently of one another, (C
1
-C
8
)-alkyl, (C
3
-C
8
)-cycloalkyl, substituted or unsubstituted aryl;
 or R
1
a and R
2
a, or R
2
a and R
3
a, or R
3
a and R
4
a, together form an aliphatic ring having from 4 to 10 carbon atoms,
 or R
5
a and R
6
a together with the P atom form a saturated or unsaturated 4- to 9-membered ring,
 or R
4
a and R
5
a form a bridging 1,&ohgr;-alkanediyl chain having from 2 to 7 carbon atoms;
 and
 Y is an anion of an inorganic or organic acid, a &agr;,&ggr;-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.
The process of the invention makes it possible to prepare, for example, biphenyls, phenylpyridines, phenylfurans, phenylpyrroles, phenylthiophenes, bipyridines, pyridylfurans and pyridylpyrroles.
Preference is given to compounds of the formula (1) in which
R
1
to R
10
are identical or different and are each hydrogen, straight-chain or branched C
1
-C
4
-alkyl, C
5
-C
6
-cycloalkyl, methyl-(C
5
-C
6
)cycloalkyl, C
2
C
4
-alkenyl, C
2
-C
4
-alkynyl, fluorine, chlorine, hydroxy, C
2
-C
4
-alkoxy, NH
2
, NHR′, NR′
2
, NHCOR′, NHCOOR′, COOH, COOR′, CN, phenyl, a phenyl, benzyl or pyridyl substituted by from 1 to 3 radicals selected from the group consisting of C
1
-C
4
-alkyl, F, Cl, C
2
-C
4
-alkoxy or NO
2
, or two adjacent radicals R
(n)
and R
(n+1)
form a 1,&ohgr;-alkyldiyl chain having from 4 to 6 carbon atoms, and
R′ is hydrogen, C
1
-C
4
-alkyl, C
1
-C
6
-alkoxy or phenyl.
Preferred aromatic boron compounds of the formula (3) are ones in which
R
6
to R
10
are as defined above and
Q
1
and Q
2
are each a radical of the formula OH, —O—(C
1
-C
4
)-alkyl, —O—(C
2
-C
4
)-alkenyl, —O—(C
2
-C
4
)-alkynyl, O-phenyl or —O-benzyl, or
Q
1
, Q
2
and the adjacent boron atom form a cyclic boric ester of the alcohols ethylene glycol, 1,3-propanediol, 1,4-butanediol, 2,2-dimethylpropane-1,3-diol, catechol, pinacol, 2,3-dihydroxynaphthalene, diethanolamine, triethanolamine, 1,2-dihydroxycyclohexane, 1,3-dihydroxycyclopentane or 1,2-dihydroxycyclooctane.
The synthesis of the catalysts of the formula (IV) is described in DE-A1-19647584. The palladaphosp

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