- C-H FLUORINATION OF HETEROCYCLES WITH SILVER (II) FLUORIDE
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The present invention provides compositions and methods for the selective C-H fluorination of nitrogen-containing heteroarenes with AgF2, which has previously been considered too reactive for practical, selective C-H fluorination. Fluorinated heteroarenes are prevalent in numerous pharmaceuticals, agrochemicals and materials. However, the reactions used to introduce fluorine into these molecules require pre-functionalized substrates or the use of F2 gas. The present invention provides a mild and general method for the C-H fluorination of nitrogen-containing heteroarene compounds to 2-fluoro-heteroarenes with commercially available AgF2. In various embodiments, these reactions occur at ambient temperature within one hour and occur with exclusive selectivity for fluorination at the 2-position. Exemplary reaction conditions are effective for fluorinating diazine heteroarenes to form a single fluorinated isomer.
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- Synthesis and late-stage functionalization of complex molecules through C-H fluorination and nucleophilic aromatic substitution
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We report the late-stage functionalization of multisubstituted pyridines and diazines at the position α to nitrogen. By this process, a series of functional groups and substituents bound to the ring through nitrogen, oxygen, sulfur, or carbon are installed. This functionalization is accomplished by a combination of fluorination and nucleophilic aromatic substitution of the installed fluoride. A diverse array of functionalities can be installed because of the mild reaction conditions revealed for nucleophilic aromatic substitutions (SNAr) of the 2-fluoroheteroarenes. An evaluation of the rates for substitution versus the rates for competitive processes provides a framework for planning this functionalization sequence. This process is illustrated by the modification of a series of medicinally important compounds, as well as the increase in efficiency of synthesis of several existing pharmaceuticals.
- Fier, Patrick S.,Hartwig, John F.
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p. 10139 - 10147
(2014/08/05)
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- Access to 2-Aminopyridines - Compounds of great biological and chemical significance
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2-Aminopyridines are key structural cores of bioactive natural products, medicinally important compounds, and organic materials and thus, extremely valuable synthetic targets. The few reported 6-substituted 2-aminopyridines and the lack of flexible, efficient and general applicable methods for their synthesis demonstrates the urgent need of new methods for their preparation. Reactions between 2,6-dibromopyridine and primary or secondary, cyclic or acyclic, and aliphatic or aromatic amines were shown to selectively yield the respective 6-bromopyridine-2-amines in very high yields which were successfully used as substrates for subsequent C-C cross-coupling reactions. The recently introduced dichloro-bis[1-(dicyclohexylphosphanyl)piperidine]palladium (1) was used as catalyst for the cross-coupling of 6-bromopyridine-2-amines with arylboronic acids, diaryl- and dialkylzinc reagents or olefins and hence, is also an excellent C-C cross-coupling catalyst for this type of substrate. Moreover, all the reaction protocols presented were in each of the catalyses uniformly applied. The scope of both the amination and the cross-coupling reactions are well defined and allow one to simply adapt the reaction protocols directly to other amines and/or coupling partners and, thus, provide for the first time a very flexible and generally applicable reaction protocol to get access to 2-aminopyridines.
- Bolliger, Jeanne L.,Oberholzer, Miriam,Frech, Christian M.
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p. 945 - 954
(2011/06/19)
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