A Structure From the Molecular Sponge

There's an interesting report from the Buchwald group using the Fujita "molecular sponge" crystallography technique. The last report on this was a correction, amid reports that the method was not as widely applicable as had been hoped, so I'm very happy to see it being used here.

They're revising the structure of a new reagent (from the Lu and Shen groups in Shanghai) for introducing the SCF3 group. It was proposed to be a hypervalent iodine (similar to other reagents in this class), but Buchwald's group found some NMR data and reactivity trends that suggested the structure might be in the open form, rather than the five-membered iodine ring one.

Soaking this reagent into the MOF crystal provided a structure, although if you read the supporting information, it wasn't easy. The compound was still somewhat disordered in the MOF lattice, and there were still nitrobenzene and cyclohexane solvent molecules present. The SCF3 reagent showed up in two crystallographically independent sites, one of them associated with residual nitrobenzene. After a good deal of work, though, they did show that open-form structure was present. (The Shen et al. paper's conclusions on its synthetic uses, though, are all still valid; it's just the the structure doesn't fall into the same series as expected).

So the MOF crystallography method lives, although I've still yet to hear of it giving a structure with a nitrogen-containing compound (which rather limits its use in drug discovery work, as you mi...

Source: In the Pipeline - March 7, 2014 Category: Chemists Tags: Chemical News Source Type: blogs