- Iodine-Catalyzed Synthesis of Chalcogenophenes by the Reaction of 1,3-Dienyl Bromides and Potassium Selenocyanate/Potassium Sulfide (KSeCN/K2S)
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The methods available for the synthesis of chalcogenophenes, in general, are associated with drawbacks of harsh conditions, use of costly metals, broad applicability, tedious purification process and low yield. To avoid these drawbacks a transition metal-free iodine-catalyzed reaction of aryl-susbstituted 1,3-dienyl bromides with potassium selenocyanate/potassium sulfide (KSeCN/K2S) leading to the corresponding selenophenes and thiophenes has been developed. Iodine is relatively benign, less expensive and readily available. Several diversely substituted selenophenes and thiophenes have been obtained by this procedure in high yields. Using this procedure 2-(4-chlorophenyl)thiophene, a key intermediate for the synthesis of a melanin concentrating hormone receptor ligand involved in the treatment of eating disorders, weight gain, obesity, depression and anxiety has been synthesized. Although the reaction is one-pot essentially it proceeds in two steps involving a selenocyanate/thiolate intermediate leading to the selenophene/thiophene. The simple operation, use of inexpensive reagents and a metal-free process make this procedure more attractive for an easy access to substituted selenophenes and thiophenes. (Figure presented.).
- Maity, Pintu,Ranu, Brindaban C.
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p. 4369 - 4378
(2017/12/26)
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- Synthesis of annulated arenes and heteroarenes involving lewis acid-mediated regioselective annulation of unsymmetrical 1,2-(Diaryl/ diheteroarylmethine)dipivalates
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A ZnBr2-mediated regioselective annulation of unsymmetrical 1,2-diarylmethinedipivalates in DCM at room temperature led to the formation of annulated arenes and heteroarenes. The annulation of the dipivalate proceeds through the intermediacy of
- Sivasakthikumaran, Ramakrishnan,Nandakumar, Meganathan,Mohanakrishnan, Arasambattu K.
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p. 9053 - 9071,19
(2012/12/12)
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- Direct 2-arylation of thiophene using low loading of a phosphine-free palladium catalyst
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The direct coupling of aryl halides with thiophene would be a considerable advantage for sustainable development because of only HBr associated with a base as by-product is formed and the number of steps to prepare these compounds is less than in more cla
- Bensaid, Souhila,Roger, Julien,Beydoun, Kassem,Roy, David,Doucet, Henri
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experimental part
p. 3524 - 3531
(2011/09/16)
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- An efficient low-temperature stille-migita cross-coupling reaction for heteroaromatic compounds by Pd-PEPPSI-IPent
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The reactivity of Pd-PEPPSI (Pyridine, Enhanced, Precatalyst, Preparation, Stabilization, and Initiation) precatalysts in the Stille-Migita crosscoupling reaction between heteroaryl stannanes and aryl or heteroaryl halides was evaluated. In general, PdPEPPSI-IPent (IPent = diisopentylphenylimidazolium derivative) demonstrated high efficiency over a variety of challenging aryl or heteroaryl halides with thiophene-, furan-, pyrrole-, and thiazole-based organostannanes when compared with Pd-PEPPSI-IPr (IPr = diisopropylphenylimidazolium derivative). The transformations proceeded at appreciably lower temperatures (3080°C) than triarylphosphine-based Pd catalysts, improving the scope of this useful carbon-carbon bond-forming process.
- Dowlut, Meenakshi,Mallik, Debasis,Organ, Michael G.
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supporting information; experimental part
p. 4279 - 4283
(2010/07/02)
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- TRIDENTATE LIGANDS AND RELATIVE COMPLEXES WITH TRANSITION METALS
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The present invention relates to tridentate ligands and the relative complexes of these ligands with transition metals. The ligands and their complexes are useful in the oligomerization and/or polymerization of ethylene and alpha-olefins. The ligands are represented by formula (I) wherein R1 is ethyl, R2, R3, R4, R5 and R6, are independently selected from the group consisting of hydrogen, halogen, C1-C10 alkyl, C6-C15 aryl, and halogenated C6-C15 aryl; R7 is selected from the group consisting of H, C1-C10 alkyl, and C6-C15 aryl; and R8 is selected from the group consisting of phenyl, alkyl substituted phenyl, C1-C10 alkyl and C6-C15 aryl.
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