Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• use as building blocks in Suzuki–Miyaura or Sonogashira coupling reactions. Keywords: boronic acid; donor/acceptor; linker; Sonogashira reaction; property tuning; push-pull; Suzuki–Miyaura reaction; Introduction Development of new organic compounds with improved and advanced properties is one of the

• triisopropyl borate followed by esterification with pinacol afforded dioxaborolanes 4b–c in the yields of 81 and 83% (Scheme 1, Method B). The biphenyl-4-boronic acid corresponding to 4a was also commercially available while 4b was reported as a side product [35] without full characterization. Whereas 5a was

Catalytic synthesis of (E)-α,β-unsaturated esters from aldehydes and 1,1-diethoxyethylene

• Rubén Manzano,
• Lidia Ozores,
• Andreas Job,
• Lars Rodefeld and
• Benjamin List

Beilstein J. Org. Chem. 2009, 5, No. 3, doi:10.3762/bjoc.5.3

• leads to the formation of water and CO2 as the only by-products (Scheme 1, eq 3) [23][24]. Here we describe as a new approach, the boronic acid-catalyzed condensation of ketene dialkyl acetal with aldehydes to furnish α,β-unsaturated esters in good yields and reliably high (E)-stereoselectivities

• this particular boronic acid, which possesses both Lewis acidity and Brønsted acidity, was the most active catalyst and gave the highest yields of the corresponding α,β-unsaturated ester. The optimized procedure involved the slow addition of 1,1-diethoxyethylene to benzaldehyde in the presence of a

• mechanism that explains the peculiar effectiveness of boronic acids as catalysts (Scheme 2). Accordingly, the boronic acid functions as a Lewis acid activating the aldehyde but also as a hydroxide donor facilitating the departure of ethanol from an activated intermediate. Clearly, alternative mechanisms may

N-Arylation of amines, amides, imides and sulfonamides with arylboroxines catalyzed by simple copper salt/EtOH system

• Zhang-Guo Zheng,
• Jun Wen,
• Na Wang,
• Bo Wu and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2008, 4, No. 40, doi:10.3762/bjoc.4.40

• recently in the mechanism of the cross-coupling reaction based on boronic acid. The group of Chan has reported the dynamic behavior of boronic acid in the copper salt catalytic system. The results implied that the active arylating agent such as arylboronic acid in the cross-coupling reaction is indeed its

A convenient catalyst system for microwave accelerated cross- coupling of a range of aryl boronic acids with aryl chlorides

• Matthew L. Clarke,
• Marcia B. France,
• Jose A. Fuentes,
• Edward J. Milton and
• Geoffrey J. Roff

Beilstein J. Org. Chem. 2007, 3, No. 18, doi:10.1186/1860-5397-3-18

• -phenyl boronic acid and 4-formyl boronic acid was investigated, since products 3 and 4 are potential intermediates in the synthesis of the clinically used drugs, Losartan and Valsartan respectively. [28][29] Under conventional heating conditions, attempts to couple 4-formyl benzene boronic acid to 2

• -chloro-benzonitrile, under conditions that gave high yields using phenyl boronic acid, gave essentially no product (<5% as determined by NMR, GC and TLC analysis). However, reactions carried out in the microwave gave good isolated yields after just 15 minutes at 140°C in acetonitrile. This reason for

• this difference in reactivity is not clear. However, a number of observations made during our studies suggested that the nature of the boronic acid nucleophile can have a major effect on the productivity of cross-coupling reactions. The majority of studies, including our own, have neglected to fully