Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1989-05-12
1992-02-11
Bond, Robert T.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568775, 568661, 570127, 570128, 570129, 562474, 562469, 558425, 546346, 546339, C07C 2513
Patent
active
050877640
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the preparation of 1,4-disubstituted 2,3-difluorobenzenes, in which 1-substituted 2,3-difluorobenzenes are deprotonated in the 4-position using an organometallic reagent and optionally reacted with an electrophile. The invention additionally relates to 1,4-disubstituted 2,3-difluorobenzenes, in particular those which are prepared according to the abovementioned process. Excluded from the invention are fluorinated oligophenyls of the formula T ##STR1## wherein the terminal substituents radicals having up to 15 C atoms optionally substituted by CN or by at least one halogen atom, wherein one or more non-adjacent CH.sub.2 groups of these radicals may also be replaced by --O--, --S--, --CO--, --O--CO--, --CO--O--, --O--CO--O--or --C.tbd.C--, one of these radicals R is also a group of the formula ##STR2## with one of the following pairs of lateral substituents both substituents are fluorine: (A, B), (C, D), (C', D') and all other lateral substituents are hydrogen or fluorine.
These compounds are the subject of the undisclosed Patent Applications P 3,807,956, P 3,807,862, GB 8,806,220 and WO 87-00515.
In preparative organic chemistry, processes for the metalation of aromatics are of increasing importance. It has been shown that in substituted aromatics regioselective metalations are possible for reasons of orientation effects. Thus, for example, 1,2- and 1,3-difluorobenzene can in each case be metalated regiospecifically in the ortho-position to give 2,3- or 2,6-difluorophenyllithium.
The lithiated compounds are stable below -50.degree. C. and represent useful intermediates in the synthesis of many difluoroaromatics (A.M. Roe, Chem. Comm. 22, 582, 1965).
It has now surprisingly been found that 2, 3-difluorobenzenes suitably substituted in the 1-position can be selectively metalated in the 4-position. 1,4-disubstituted 2,3-difluorobenzenes can thus be prepared either by deprotonating 2,3-difluorobenzenes substituted in the 1-position with an organometallic reagent and optionally reacting with an electrophile or, starting from 1,2-difluorobenzene, initially deprotonating in the one ortho-position, as described above, then reacting with an electrophile and subsequently repeating the process in the second ortho-position (ortho to F) with a second equivalent of base and, if desired, an electrophile.
The compounds obtainable by these processes are, depending on substitution, useful intermediates in the synthesis of liquid crystalline compounds or compounds which, as components of liquid crystalline phases, improve the dielectric anisotropy or other parameters of the latter. However, they are very generally of interest as intermediates in industrial organic chemistry.
The invention therefore relates to a process for the preparation of 1,4-disubstituted 2,3-difluorobenzenes, excluding fluorinated oligophenyls of the formula T ##STR3## wheein the terminal substituents radicals having up to 15 C atoms optionally substituted by CN or by at least one halogen atom, wherein one or more non-adjacent CH2 groups of these radicals may be replaced by --O--, --S--, --CO--, --O--CO--, --CO--O--, --O--CO--O--or --C.tbd.C--, one of these radicals R is also a group of the formula ##STR4## with one of the following pairs of lateral substituents both substituents are fluorine: (A, B), (C, D), C', D) and all other lateral substituents are hydrogen or fluorine, characterized in that 1-substituted 2,3-difluorobenzenes are deprotonated in the 4-position using an organometallic reagent and optionally reacted with an electrophile.
The invention also relates to compounds of the formula I ##STR5## wherein Q is ##STR6## R.sup.2 is H or an alkyl or alkenyl radical each having 1 to 15 C atoms, wherein one or more non-adjacent CH.sub.2 groups may be replaced by 0 atoms, --COR.sup.4, --CO--OR.sup.4 or --O--COR.sup.4, --CH.sub.2 O--, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C-- or a single bond, groups may be replaced by 0 atoms, N, piperidine-1,4-diyl, bicyclo(2,2,2)-octylene, naphthalene-2,6-diyl, decahyd
REFERENCES:
patent: 4366330 (1982-12-01), Gray et al.
patent: 4429153 (1984-01-01), Punja
Krause Joachim
Reiffenrath Volker
Bond Robert T.
Merck Patent Gesellschaft mit beschrankter Hafung
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