A magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdII nanocomposite exhibiting facile tandem Suzuki coupling/transfer hydrogenation reaction

Herein, we report a magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdIINP (5) nanocomposite system for tandem Suzuki coupling/transfer hydrogenation reaction. The nanocomposite 5 was prepared first by making a layer of $$\hbox {SiO}_{2}$$ SiO 2 on $$\hbox {Fe}_{3}\hbox {O}_{4}\hbox {NP}$$ Fe 3 O 4 NP followed by deposition of $$\hbox {Pd}^{0}$$ Pd 0 and sorption of $$\hbox {Pd}^{\mathrm{II}}$$ Pd II ions successively onto the surface of Fe3O4@SiO2NP. The nanocomposite was characterized by powder XRD, electron microscopy (SEM-EDS and TEM-EDS) and XPS spectroscopy techniques. The mixed-valent $$\hbox {Pd}^{0}/\hbox {Pd}^{\mathrm{II}}$$ Pd 0 / Pd II present onto the surface of nanocomposite 5 was confirmed by XPS technique. Interestingly, the mixed-valent nanocomposite Fe3O4@SiO2/Pd0/PdIINP (5) exhibited tandem Suzuki coupling/transfer hydrogenation reaction during the reaction of aryl bromide with aryl boronic acid (90% of C). The nanocomposite 5 displayed much better reactivity as compared to the monovalent Fe3O4@SiO2/Pd0NP (3) (25% of C) and Fe3O4@SiO2/PdIINP (4) (15% of C) nanocomposites. Further, because of the presence of magnetic $$\hbox {Fe}_{3}\hbox {O}_{4}$$ Fe 3 O 4 , the nanocomposite displayed its facile separation from the reaction mixture and reused at least for five catalytic cycles.

Convergent Synthesis of Angiotensin II Receptor Blockers through C-H Arylation with Functionalized Aryl Bromides

Highly convergent synthesis of Angiotensin II receptor blockers has been accomplished by means of late stage C-H arylation using functionalized aryl bromides. C-H arylation of phenyl tetrazole with aryl bromide carrying methyl 2-ethoxy-benzimidazole-7-carboxylate unexpectedly provided coupling product where ethyl group was migrated from oxygen to nitrogen atom. The <i>O</i>- to <i>N</i>-ethyl migration was completely suppressed by the use of <i>N</i>-pivaloyl-L-valine rather than the combined use of triphenyl phosphine and sodium mesitylenesulfonate to result in the preferential formation of a key intermediate of candesartan cilexetil. In contrast, when an aryl bromide having ethyl 4-(1-hydroxy-1-methylethyl)-2-propylimidazole-5-carboxylate was employed, the C-H arylation proceeded smoothly to provide a late stage intermediate which was rapidly led to olmesartan medoxomil in 3 steps.

Mechanistic understanding of the Cu(i)-catalyzed domino reaction constructing 1-aryl-1,2,3-triazole from electron-rich aryl bromide, alkyne, and sodium azide: a DFT study

The mechanism of the Cu(i)-catalyzed domino reaction furnishing 1-aryl-1,2,3-triazole assisted by CuI and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is explored with density functional theory (DFT) calculations.

Synthesis of Polycyclic Ether-Benzopyrans and In Vitro Inhibitory Activity against Leishmania tarentolae

Construction of a focused library of polycyclic ether-benzopyrans was undertaken in order to discover new therapeutic compounds that affect Leishmania growth and infectivity. This is especially of interest since there are few drug therapies for leishmaniasis that do not have serious drawbacks such high cost, side effects, and emerging drug resistance. The construction of these polycyclic ether-benzopyrans utilized an acetoxypyranone-alkene [5+2] cycloaddition and the Suzuki-Miyaura cross-coupling. The multi-gram quantity of the requisite aryl bromide was obtained followed by effective Pd-catalyzed coupling with boronic acid derivatives. Compounds were tested in vitro using the parasitic protozoan, Leishmania tarentolae. Effects of concentration, time, and exposure to light were evaluated. In addition, the effects on secreted acid phosphatase activity and nitric oxide production were investigated, since both have been implicated in parasite infectivity. The data presented herein are indicative of disruption of the Leishmania tarentolae and thus provide impetus for the development and testing of a more extensive library.