A Window into Cyclization

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Science  19 Sep 2008:
Vol. 321, Issue 5896, pp. 1607
DOI: 10.1126/science.321.5896.1607a

Few carbon-based compounds absorb light in the visible portion of the spectrum. Organic photochemical reactions therefore largely rely on irradiation in the ultraviolet, which is expensive to implement on a large scale and often introduces substantial excess energy into the system, which limits selectivity. At the same time, there is a multitude of metal-bearing molecules that absorb efficiently in the visible and have been studied thoroughly in the context of electron-transfer chemistry.

Ischay et al. applied one such compound, a ruthenium (Ru) complex bearing three bipyridyl ligands, toward the catalysis of enone cyclization. The substrates are two tethered C=C-C(O)-R moieties, where at least one R group must be a phenyl ring (the other can be an alkyl, alkoxy, or amide group). Upon absorbing blue light, the Ru complex can undergo an electron-transfer cycle that lends an electron to the substrate, accelerating formation of a bicyclic product via bond formation between the olefins. Placing the reaction flask by the window is sufficient for ordinary sunlight to drive the process. — JSY

J. Am. Chem. Soc. 130, 10.1021/ja805387f (2008).

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