Beilstein J. Org. Chem.2012,8, 2132–2141, doi:10.3762/bjoc.8.240
Pankaj Chauhan Swapandeep Singh Chimni U.G.C. Sponsored Centre for Advance Studies in Chemistry, Department of Chemistry Guru Nanak Dev University, Amritsar, 143005, India, Fax: (+)91-183-2258820 10.3762/bjoc.8.240 Abstract Ball-milling and pestle and mortar grinding have emerged as powerful
: ball-milling; enantioselective synthesis; mechanochemistry; organocatalysis; solvent-free; Introduction
Green chemistry involves innovation in chemical research and engineering that encourages the design of processes to minimize the use and production of hazardous materials and also reduce the use of
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To address many of these issues mechanochemical methods such as ball-milling and grinding with pestle and mortar have emerged as powerful techniques [5][6][7][8][9][10][11][12]. The mechanical energy generated by grinding two solids or one solid and one liquid substance results in the formation of
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Graphical Abstract
Scheme 1:
Proline-catalysed aldol reaction in a ball-mill.
Beilstein J. Org. Chem.2010,6, No. 7, doi:10.3762/bjoc.6.7
the above mentioned parameters on the results of coupling reactions. The results from ballmilling experiments led to the conclusion that self-prepared and commercially available KF–Al2O3 differ in water content. The higher the residual water content, the higher are the product yields.
Keywords: ball
couplings applying ballmilling conditions [55][56], respectively, the reaction times were substantially reduced from several hours to a few minutes following the present reaction protocol.
A comparison of the results from the Suzuki–Miyaura coupling of 1 with p-bromoacetophenone (2a) assisted by pure
titanium silicalite, TiSiO4, showed moderate conversions in the range of basic γ-Al2O3 SRS3. Contrary to microwave-assisted reactions, MgO showed only little conversion when used as a base under ballmilling conditions [34], whereas neutral oxides SiO2 and CeO2 did not show any conversion. Since the
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Graphical Abstract
Scheme 1:
Suzuki–Miyaura reaction of phenylboronic acid (1) with aryl bromides 2 yielding substituted biaryls ...