Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1996-02-01
1998-07-28
Shah, Mukund J.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
548123, 548950, 564 82, C07D28516, C07D28500, C07D20500, C07C30300
Patent
active
057864748
DESCRIPTION:
BRIEF SUMMARY
This is a 371 application of PCT/EP 94/01251 filed on Apr. 20, 1994.
this invention relates to N-fluorosulfonimides, which are suitable as fluorinating reagents.
In the search for new pharmaceutical or agrochemical products, fluorinated substances have great importance. For the production of these compounds, electrophilic fluorinating reagents play a special role since they make it possible to exchange activated hydrogens with fluorine in one step. Known reagents of this type are, i.e., the gas perchloryl fluoride, which tends toward reactions that are too explosive, cesium peroxofluorosulfate, which is very difficult to store, the unstable acetyl hypofluorite, the very reactive perfluoromethane-sulfonimide, N-fluorophenyl sulfonimide (E. Differding and H. Ofner, "Synlett," p. 187, 1991), and N-fluoro-ortho-benzodisulfonimide (F. A. Davis and W. Han, "Tetrahedron Letters" 32, p. 1631, 1991).
Although with N-fluorophenyl sulfonimide, a readily manageable, easily accessible reactive agent for electrophilic fluorination is available, its content of 60.2 g of active fluorine/kg of fluorinating agent (formula weight of N-fluorophenyl sulfonimide 315.3 g/mol) is relatively low.
The object of this invention is to provide new compounds for more effective use as fluorinating agents for the electrophilic fluorination of activated C--H bonds.
It has now been found that the new N-fluorosulfonimides of general formula I
R.sup.1 means a methyl group each or together a group --(CH.sub.2).sub.n --with n=1, 2 or 3, fluorination of activated C--H bonds.
Within the scope of this invention, N-fluoromethane-sulfonimide and
The fluorosulfonimides of general formula I according to the invention exhibit a higher active fluorine content because of their considerably lower formula weight as compared with N-fluorophenylsulfonimide; for example, the N-fluoromethane-sulfonimide according to the invention with a formula weight of 191.2 g/mol has an active fluorine content of 99.3 g of fluorine/kg.
The compounds of general formula I are readily soluble in many organic solvents. The sulfonimide that remains after fluorination from the active compound has significantly better water solubility than phenylsulfonimide. As a result, the sulfonimide that is formed in each case can be separated quite simply by washing the organic phase, for example, diethyl ether, in which the fluorinated product is present. Expensive chromatographic purification steps and the use of large amounts of solvent are thus avoided.
It is considered surprising that the compounds of general formula I according to the invention, such as the known N-fluorophenylsulfonimide, are stable. In the case of the compounds of general formula I, it would actually have been expected that the very reactive fluorine would be transferred intramolecularly and/or intermolecularly to radical R.sup.1 and that the compounds of general formula I would fluorinate themselves, as it were.
The production of the N-fluorosulfonimides of general formula I is done according to the invention by reacting the easily accessible sulfonimides of general formula II
R.sup.1 means a methyl group each or together a group --(CH.sub.2).sub.n --with n=1, 2 or 3,
Acetonitrile is preferably used as solvent. The reaction temperature is between 0.degree. C. and -50.degree. C.; it is preferably -40.degree. C. fluorination is preferably done in the presence of an alkali fluoride, such as, for example, sodium fluoride, and if necessary, the product can be purified chromatographically (SiO.sub.2 eluent, e.g., CH.sub.2 CL.sub.2).
Advantageously, the N-fluorosulfonimides according to the invention can be used for fluorination of activated C--H bonds in aromatic compounds, enol ethers, enolates or arylates. In this case, the procedure according to the invention is normally such that the corresponding C--H bond is first deprotonated by reacting the substrate with a strong base, such as, for example, sodium hydride, lithium diisopropylamide, or an alkyllithium compound, such as, for example, tert-butyllithium, and the thus
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Ngo Tamthom T.
Schering Aktiengesellschaft
Shah Mukund J.
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