Chemistry

Upside of a Double Negative

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Science  30 May 2008:
Vol. 320, Issue 5880, pp. 1134
DOI: 10.1126/science.320.5880.1134a

Chemical bonds tend to form most easily by the attack of an ion on an oppositely polarized center, or by the neutral interactions of radical centers bearing unpaired electrons. Bisai et al. took the somewhat counterintuitive approach of preparing two negatively charged sites and then adding an oxidant to draw them together. The deprotonation of both a carbon and a nitrogen center came at a late stage in the synthesis of the polycyclic organic natural product lyconadin A. When more traditional approaches toward linking C and N to close the ring had failed, the authors relied on the likelihood that a lithium cation would stabilize a dianion through simultaneous coordination to both centers. Treatment with iodine then induced C-N bond formation in 80% yield, affording an impressive overall product yield of 10% over the 18 steps of the synthesis. — JSY

J. Am. Chem. Soc. 130, 10.1021/ja8028069 (2008).

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