- Pd-catalyzed oxidative homocoupling of arylboronic acids in WEPA: A sustainable access to symmetrical biaryls under added base and ligand-free ambient conditions
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Symmetrical and unsymmetrical biaryls comprises a diverse class of biologically eloquent organic compounds. We herein report, a quick and eco-friendly protocol for the synthesis of biaryls by an oxidative (aerobic) homocoupling of arylboronic acids (ABAs) using Pd(OAc)2 in water extract of pomogranate ash (WEPA) as an efficient agro-waste(bio)-derived aqueous (basic) media. The reactions were executed at ambient aerobic conditions in the absence of external base and ligand to result symmetrical biaryls in excellent yields. The use of renewable media with an effective exploitation of waste, short reaction times, excellent yields of products, easy separation of the products, unnecessating the external base, oxidant, ligand or volatile organic solvents and ambient reaction conditions are the vital insights of the present protocol.
- Appa, Rama Moorthy,Lakshmidevi, Jangam,Naidu, Bandameeda Ramesh,Venkateswarlu, Katta
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- A shape-persistent macrocycle with two opposing 2,2':6',2'-Terpyridine units
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The synthesis reported here of the shape-persistent macrocycle 9 with two opposing terpyridine units, and with pendant flexible chains for solubility reasons, was achieved by Suzuki cross-coupling of two 'half-cycles', the bisboronic acid ester 7 and its diiodo counterpart 8. Cycle 9 was obtained on a 100 mg scale in a yield of 20%. It was characterized by FAB mass spectrometry and 1H and 13C NMR spectroscopy. Cycle 9 is the first shape-persistent cycle containing terpyridine units that is larger than cyclosexipyridine. An improved synthesis of the important building block dibromoterpyridine 12 is also presented.
- Lehmann, Uwe,Dieter Schlueter
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p. 3483 - 3487
(2007/10/03)
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