Functionalization of diazines and benzo derivatives through deprotonated intermediates.

International audienceThis critical review targets as a readership researchers generally oriented toward organic synthesis and in particular those active in heterocyclic chemistry. Diazines and benzo derivatives can undergo deprotonative metalation provided that the base is properly chosen. Metalation reactions of a large range of substrates can be performed using hindered lithium dialkylamides such as lithium 2,2,6,6-tetramethylpiperidide. Subsequent reactions with electrophiles open an entry to a great variety of building blocks, notably for the synthesis of biologically active compounds. (83 references)

TMP-cadmiate: A base for Efficient and Chemoselective Deprotonative Metallation Reactions of Aromatic Compounds

International audienceEfficient deprotonative cadmiation reactions of functionalized aromatics including heterocycles have been realized using TMP-cadmiate, (TMP)3CdLi (TMP = 2,2,6,6-tetramethylpiperidino). The reagent is compatible with reactive functional groups (amide, ester, nitrile and even ketone functions), heavy halogens (Br, I), five-membered aromatic heterocycles (furan, thiophene, oxazole, thiazole, and pyrrole derivatives) and even aromatic aza-heterocycles (pyridine, diazine compounds). Some heterocycles benefiting from doubly activated positions can be dimetallated at room temperature. The deprotonative cadmiation pathways/mechanisms have been studied using computational/theoretical techniques. The lithium arylcadmiates such generated have been evidenced using iodine. Alternative trappings of the species are palladium-catalyzed cross-coupling reactions or simple quench with acid chlorides

Pyridine Elaboration through Organometallic Intermediates: Regiochemical Control and Completeness

International audiencePyridines carrying heterosubstituents (such as carboxy, amido, amino, alkoxy or trifluoromethyl groups or solely individual halogen atoms) can be readily and site selectively metalated. Subsequent reaction with a suitable electrophile opens rational access to a wealth of new building blocks for the synthesis of biologically active compounds. This approach relies on organometallic methods, which are both efficacious and extremely flexible as far as the substitution site and the product structure are concerned

Ionic-Liquid-Supported Synthesis of Amines and Derivatives

International audienceAmine precursors such as glycines protected at nitrogen with a Boc or formyl group were grafted by esterification on the hydroxylated arms of 1-(2-hydroxyethyl)-3-methylimidazolium hexafluorophosphates or tetrafluoroborates. The cleavage of the Boc group was then realized at room temperature by successively treating acetonitrile solutions of the thus formed glycinates with methanol and acetyl chloride (two equivalents each). Interestingly, the resulting glycinate hydrochlorides were converted into the corresponding amines during the removal of the solvent. Ugi reaction of one of these ionic-liquid-grafted amines with phthalaldehydic acid and tert-butyl isocyanide, followed by cleavage, furnished a phthalimidine 12

Palladium-Catalyzed Cross-couplings of Lithium Arylzincates with Aromatic Halides. Synthesis of Analogues of Isomeridianin G and Evaluation as GSK- 3 Inhibitors

International audienceSeveral analogues of Isomeridianin G have been synthesized using as a key step palladium-catalyzed crosscoupling reactions of lithium triorganozincates. The latter have been prepared by deprotonative lithiation followed by transmetalation using ZnCl2*TMEDA (1/3 equiv)

Synthesis of Unsymmetrical Heterobiaryls Using palladium-catalyzed cross-coupling reactions of lithium organozincates

International audienceSeveral unsymmetrical heterobiaryls have been synthesized through palladium-catalyzed cross-coupling reactions of lithium triorganozincates. The latter have been prepared by deprotonative lithiation followed by transmetalation using non hygroscopic ZnCl2*TMEDA (1/3 equiv)

Deprotonative metalation of substituted aromatics using mixed lithium-cobalt combinations

International audienceThe deprotonation of anisole was attempted using different homo- and heteroleptic TMP/Bu mixed lithium-cobalt combinations. Using iodine to intercept the metalated anisole, an optimization of the reaction conditions showed that in THF at room temperature 2 equiv of base were required to suppress the formation of the corresponding 2,2'-dimer. The origin of the dimer was not identified, but its formation was favored with allyl bromide as electrophile. The metalated anisole was efficiently trapped using iodine, anisaldehyde, and chlorodiphenylphosphine, and moderately employing benzophenone, and benzoyl chloride. 1,2-, 1,3- and 1,4-dimethoxybenzene were similarly converted regioselectively to the corresponding iodides. It was observed that 2-methoxy- and 2,6-dimethoxypyridine were more prone to dimerization than the corresponding benzenes when treated similarly. Involving ethyl benzoate in the metalation-iodination sequence showed the method was not suitable to functionalize substrates bearing reactive functions

New Gilman-type lithium cuprate from a copper(II) salt: synthesis and deprotonative cupration of aromatics

International audienceDeprotonative cupration of aromatics including heterocycles (anisole, 1,4-dimethoxybenzene, thiophene, furan, 2- fluoropyridine, 2-chloropyridine, 2-bromopyridine and 2,4-dimethoxypyrimidine) was realized in tetrahydrofuran at room temperature using the Gilman-type amido-cuprate (TMP)2CuLi in situ prepared from CuCl2*TMEDA through successive addition of 1 equivalent of butyllithium and 2 equivalents of LiTMP. The intermediate lithium (hetero)arylcuprates were evidenced by trapping with iodine, allyl bromide, methyl iodide and benzoyl chlorides, the latter giving the best results. Symmetrical dimers were also prepared from lithium azine and diazine cuprates using nitrobenzene as oxidative agent

Novel chromophores from alternated pyridine–ethylenedioxythiophene unit oligomers: dramatic enhancement of photoluminescence properties in elongated derivatives

C. Katan present address: CNRS UMR6082 FOTON, INSA de Rennes, 20 avenue des Buttes de Coësmes, CS 70839, 35708 RENNES cedex 7, FranceInternational audienceNovel chromophores based on the alternation of electron-poor (pyridyl) and electron-rich (ethylenedioxythienyl) heterocycles were synthesized for the first time and shown to exhibit attractive optical properties in relation with their specific electronic and geometrical (coiled structure) features

Synthesis of 2,5-Diiodopyrazine by Deprotonative Dimetalation of Pyrazine

International audienceThe deproto-metalation reactions of pyrimidine and pyrazine were regioselectively carried out using lithium tri(2,2,6,6-tetramethylpiperidino)cadmate in tetrahydrofuran at room temperature. This result was demonstrated by subsequent trapping with iodine to afford 4-iodopyrimidine and iodopyrazine in 71 and 63% yields, respectively. The same reaction performed on pyri-dazine afforded a mixture of the 3- and 4-iodo derivatives (55 and 41% yields, respectively). From pyrazine, the access to the 2,5-diiodo derivative (40% on a 25 mmol scale) proved possible using a larger amount of base (1 equiv instead of 1/3)