
The eco-sustainable "chemistry on the window ledge" of Prof. M. Fagnoni
Cheap reagents, no external energy (no artificial irradiation, no cooling, no stirring), a catalyst with high turnover, high yield, single peak in GC, low environmental impact. The Holy Grail? Perhaps, but this is exactly what Prof. M. Fagnoni and coworkers at the University of Pavia (Italy) report for the functionalization of a series of electrophilic olefines.
The strategy comprises the use of tetrabutylammonium decatungstate (TBADT), a cluster with formula (n-Bu4N)4W10O32, as photocatalyst. TBADT efficiently absorbs in the UV-A region and, in the excited state, abstracts an H atom from alkanes, aldehydes, ethers and amides. The radical left behind adds to electrophilic alkenes for alkylation or acylation (see picture). At the end of the cycle, TBADT-H·gives back the H atom yielding the product and regenerating the catalyst. The reactions, carried out on a window ledge under a few days of sunlight irradiation, have yields ranging from 50 to 90%, a value that in most cases is larger than that obtained using lamps.
But most importantly, compared with traditional photochemical syntheses, “chemistry on the window ledge” under optimized conditions is considerably more eco-friendly, according to environmental indices. And because reactions remains clean at higher concentrations (up to 0.5 M), production costs are significantly abated.
As migration to eco-sustainable chemical productions becomes more and more pressing, photochemistry is projected to play a pivotal role. After all, photons are “the ideal green reagent” as the authors observe, and this study demonstrates.
[“Solar Light-driven Photocatalyzed Alkylations. Chemistry on the Window Ledge”, S. Protti, D. Ravelli, M. Fagnoni, A. Albini, Chem. Commun. 2009, 7351-7353.]
Posted by Alberto 
Posted by Alberto 
Posted by Alberto 
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