C-H, N-H Coupling of azoles takes place with several amines in the presence of a copper catalyst to undergo amination at the 2-position. The reaction of benzothiazole with N-methylaniline in the presence of sodium acetate and 20 mol % Cu(OAc)(2) in xylene under an oxygen atmosphere afforded the aminated product in 81% yield.
Mechanistic studies on palladium-catalyzed CH arylation of thiophenes which has been shown by our group are carried out by a stoichiometric reaction of organometallic complexes. The reaction of arylpalladium(II) halide with 2,3-dibromothiophene in the presence of AgNO 3 /KF as an activator induces electrophilic substitution at the CH bond of the thiophene to give CH arylated product. The similar reaction of arylplatinum(II) halide with thiophene derivatives affords the aryl(thienyl)platinum(II) complex which is an analog of a precursor of the product of the CH arylation reaction. These results suggest that the palladium-catalyzed CH arylation reaction of thiophenes proceeds through electrophilic substitution.Transition-metal-catalyzed CH functionalization 1,2 attracts considerable attention as an alternative and more straightforward pathway to form a carboncarbon bond compared to transition-metal-catalyzed coupling of aryl halides with organometallic reagents.3 In particular, CH substitution reactions of heteroaromatic compounds increase their significance since compounds bearing a heteroaromatic moiety are promising for advanced materials such as organic thin film transistors (TFTs) and light-emitting devices. 4 In order to develop further practical and efficient catalytic CH substitution reactions, mechanistic understanding of the reaction is very important.We have shown that CH arylation of 2-bromothiophene (1a) with aryl iodide takes place in the presence of a palladium catalyst and AgF or AgNO 3 /KF to give aryl(bromo)thiophene. 5 It is noteworthy that the catalytic reaction of bromothiophene proceeds smoothly with the carbonbromine bond remaining intact (eq 1).
High-energy X-ray diffraction measurements were carried out for liquid 2-aminoethanol (NH2CH2CH2OH, MEA) in order to obtain direct information on the conformation of MEA in the liquid state, in which competition between intra- and intermolecular hydrogen bonds might occur. Least-squares fitting analysis was applied to the high-Q region of the observed total interference term with excellent statistical accuracies. Independent parameters, the C–C, C–O, and C–N interatomic distances, bond angles, ∠OCC and ∠CCN, and a dihedral angle ∠(NCC)–(CCO), were successfully obtained. It has been concluded that the MEA molecule takes the gauche conformation with the dihedral angle ∠(NCC)–(CCO) = 53(3)°, suggesting the formation of the intramolecular hydrogen bond is dominant in the liquid state.
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