Catechols as Sources of Hydrogen Atoms in Radical Deiodination and Related Reactions

Abstract

When used with trialkylboranes, catechol derivatives, which are low‐cost and low toxicity, are valuable hydrogen atom donors for radical chain reactions involving alkyl iodides and related radical precursors. The system 4‐tert‐butylcatechol/triethylborane has been used to reduce a series of secondary and tertiary iodides, a xanthate, and a thiohydroxamate ester. Catechol derivatives are right in the optimal kinetic window for synthetic applications, as demonstrated by highly efficient radical cyclizations. Cyclizations leading to the formation of quaternary centers can be performed in an all‐at‐once process (no slow addition of the hydrogen atom donor) at standard concentrations. The H‐donor properties of catechol derivatives can be fine‐tuned by changing their substitution pattern. In slow radical cyclization processes, an enhanced ratio of cyclized/uncyclized products was obtained by using 3‐methoxycatechol instead of 4‐tert‐butylcatechol.

Light-driven post-translational installation of reactive protein side chains

“…3c). The Lys-'guided' nature of this crosslinking was consistent with zero crosslinking from incubations with other proteins: neither Cys-rich serum albumin nor the known nucleosomal binding partner histone H4-H3•H4 PPI involves Lys 4,9,27,44 , whereas the H3•KDM4A PPI does 43 . This seeming PPIselective reaction was further confirmed by MS/MS analysis (Fig.…”

“…By mimicking the binding of Lys side chains more closely, it was possible to probe even buried PPIs without artefacts. We tested potential buried 43 and transient (substrate•enzyme) PPIs using Bhn (1u) at three sites (4,9,27) that are normally occupied by Lys in C-terminally FLAG-HA-tagged histone eH3.1. When incubated with a partner enzyme that processes (and so binds) Lys, Lysdemethylase-KDM4A was observed to crosslink exclusively to Bhn-containing eH3.1-Bhn4, eH3.1-Bhn9 and eH3.1-Bhn27, but not to WT histone eH3.1 (Fig.…”

Radical Deuteration with D2O: Catalysis and Mechanistic Insights

“…Finally, a primary alkyl iodide was tested (Table , entry 12). As anticipated, the deuterated compound was obtained in lower yield (43%) due to a slower iodine atom transfer between the ethyl radical and the substrate but with a good level of deuterium incorporation. The mechanism of the deiodination process is depicted in Scheme .…”

Catalytic Generation of Radicals from Nitroalkanes

“…Substrate 1m , prepared via the dearomative [2+3] cyclization of 3-nitroindole, 9b also underwent the reductive denitration in high yield under atmospheric conditions using phenylmethanethiol ( 2c ) as the hydrogen donor to facilitate HAT. 16…”