intermediates heterocyclic Halide chemicals cyan chemicals boronic chemicals sulfon chemicals

An efficient synthesis of sulfonyl carbamates and sulfonyl ureas from sulfonyl azides employing a palladium-catalyzed carbonylation protocol has been developed. Using a two-chamber system, sulfonyl azides, PdCl2, and CO gas, released ex situ from Mo(CO)6, were assembled to generate sulfonyl isocyanates in situ, and alcohols and aryl amines were exploited as nucleophiles to afford a broad range of sulfonyl carbamates and sulfonyl ureas. A protocol for the direct formation of substituted sulfonamides from sulfonyl azides and amines via nucleophilic substitution was also developed.
Efficient hydrochlorination of 2-ethynylpyridines was achieved without the use of special reagents. Ethynylpyridine readily reacts with hydrochloric acid to form a pyridinium salt. The salt formation considerably enhances the electrophilicity of the ethynyl group and attracts a chloride ion as the counteranion. The spatial proximity facilitates the nucleophilic addition of the halide anion to the ethynyl group, producing 2-(2-chloroethenyl)pyridine in high yields. This protocol could also be applied for hydrobromination and hydroiodination using hydrobromic and hydroiodic acids, respectively. In the case of acetic acid, the reaction did not proceed because of the low acidity and lack of salt formation. This problem was overcome by exchanging the counteranion using silver acetate; the resultant pyridinium acetate underwent hydroacetoxylation.
An efficient copper-catalyzed domino halogen exchange-cyanation procedure for aryl bromides was developed utilizing 10 mol % CuI, 20 mol % KI, 1.0 equiv of the inexpensive N,N-dimethylethylenediamine as ligand, and 1.2 equiv of NaCN in toluene at 110 .The new method represents a significant improvement over the traditional Rosenmund;von Braun reaction 8201; the reaction conditions are much milder, and the use of stoichiometric amounts of copper(I) cyanide and polar solvents is avoided; therefore the isolation and purification of the aromatic nitrile products is greatly simplified. In addition, the new method exhibits excellent functional group compatibility comparable to that of the analogous Pd-catalyzed cyanation methodology.
the reductive elimination of haloarene from {Pd[P(o-tol)3](Ar)(μ-X)}2 (X = Cl, Br, I) upon addition of the strongly electron-donating, but sterically hindered, phosphine P(t-Bu)3 and related ligands. Reductive elimination of aryl chlorides, bromides, and iodides from these dimeric arylpalladium(II) halide complexes was observed upon the addition of P(t-Bu)3. Conditions to observe the elimination and addition equilibria were established for all three halides, and values for these equilibrium constants were measured. Reductive elimination of aryl chlorides was most favored thermodynamically, and elimination of aryl iodide was the least favored. However, reactions of the aryl chloride complexes were the slowest. Detailed mechanistic data revealed that cleavage of the starting dimer, accompanied by ligand substitution either before or after cleavage, led to the formation of a three-coordinate arylpalladium(II) halide monomer that reductively eliminated haloarene.
The 5-bromopyridyl-2-magnesium chloride (2), which was not accessible previously, was efficiently synthesized for the first time via an iodo-magnesium exchange reaction with 5-bromo-2-iodopyridine (1). This reactive intermediate was allowed to react with a variety of electrophiles to afford a range of useful functionalized pyridine derivatives. Application of this methodology to 5-bromo-2-iodo-3-picoline provided a simple and economical synthesis of a key intermediate for the preparation of Lonafarnib, a potent anticancer agent.
Microwave irradiation of certain chloro-, bromo-, trifluoromethanesulfonyloxy- and nonafluorobutanesulfonyloxy-substituted quinolines in the presence of acetic anhydride and sodium iodide leads, via a trans-halogenation process, to the corresponding iodides in high yield. Related conversions involving pyridines and isoquinolines can also be achieved under similar conditions
Cobalt-catalyzed reactions of haloalkanes with dimethylphenylsilylmethylmagnesium chloride result in highly regioselective dehydrohalogenation. The reaction does not follow the conventional E2 elimination mechanism but includes β-hydride elimination from the corresponding alkylcobalt intermediate. The interesting reaction mechanism of the cobalt-catalyzed dehydrohalogenation offered unique transformations that are otherwise difficult to attain.
A rapid and general access to ortho-haloaminoarenes has been developed by aryne insertion into N-chloramine, N-bromoamine, and N-iodoamine bonds via two complementary protocols harnessing fluoride-promoted 1,2-elimination of ortho-trimethylsilyl aryltriflates. Typically, electron-deficient N-chloramines effectively react with aryne intermediates generated at elevated temperature with CsF, while less stable N-haloamines are found more efficient under milder, TBAF-mediated aryne formation at room temperature. Both protocols demonstrate a good level of regioselectivity and functional group tolerance. Efforts to elucidate the mechanism of N-X insertion are also discussed. The practical value of this transformation is highlighted by rapid synthesis of novel analogues of the antipsychotic cariprazine.
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