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Hydrodealkenylative C(sp3)–C(sp2) bond fragmentation

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Science  17 May 2019:
Vol. 364, Issue 6441, pp. 681-685
DOI: 10.1126/science.aaw4212

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Excising an olefin

Plants produce an abundance of structurally complex terpene compounds that are useful precursors to pharmaceuticals and other fine chemicals. However, the carbon frameworks of these compounds constrain the available pathways for diversification. Smaligo et al. now show that successive treatment with ozone, an iron oxidant, and a hydrogen-atom donor can cleanly cleave pendant olefins from terpenes and related compounds (see the Perspective by Caille). Breaking the bond between saturated and double-bonded carbon centers offers a direct route to desirable chiral intermediates from readily available, inexpensive precursors.

Science, this issue p. 681; see also p. 635

Abstract

Chemical synthesis typically relies on reactions that generate complexity through elaboration of simple starting materials. Less common are deconstructive strategies toward complexity—particularly those involving carbon-carbon bond scission. Here, we introduce one such transformation: the hydrodealkenylative cleavage of C(sp3)–C(sp2) bonds, conducted below room temperature, using ozone, an iron salt, and a hydrogen atom donor. These reactions are performed in nonanhydrous solvents and open to the air; reach completion within 30 minutes; and deliver their products in high yields, even on decagram scales. We have used this broadly functionality tolerant transformation to produce desirable synthetic intermediates, many of which are optically active, from abundantly available terpenes and terpenoid-derived precursors. We have also applied it in the formal total syntheses of complex molecules.

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