Abstract
AbstractNickel boride catalyst prepared in situ from NiCl2 and sodium borohydride allowed, in the presence of an aqueous solution of TEMPO-oxidized nanocellulose (0.01 wt%), the reduction of a wide range of nitroarenes and aliphatic nitro compounds. Here we describe how the modified nanocellulose has a stabilizing effect on the catalyst that enables low loading of the nickel salt pre-catalyst. Ni-B prepared in situ from a methanolic solution was also used to develop a greener and facile reduction of organic azides, offering a substantially lowered catalyst loading with respect to reported methods in the literature. Both aromatic and aliphatic azides were reduced, and the protocol is compatible with a one-pot Boc-protection of the obtained amine yielding the corresponding carbamates. Finally, bacterial crystalline nanocellulose was chosen as a support for the Ni-B catalyst to allow an easy recovery step of the catalyst and its recyclability for new reduction cycles.
Highlights
Tions[3] using both precious metals and cheaper, more abundant metals (Scheme 1)
With the aim of designing a sustainable reaction, the catalyst loading was successfully lowered to 0.5 mol%, representing a substantial improvement on respect of already existing methodologies catalyzed by cheap and abundant transition metal.[36,37]
The reaction system was proved to be general for both aliphatic and aromatic azide and a wide range of azides were tested in an attempt to highlight the limits of the reaction system as well as its functional group tolerability
Summary
Tions[3] using both precious metals (gold,[4] platinum,[5,6] palladium5,7) and cheaper, more abundant metals (e.g., cobalt,[8] nickel,[9] iron10) (Scheme 1). Giampiero Proietti obtained his M.Sc. from ‘La Sapienza University of Rome’ in 2015 with a thesis work on the synthesis of a photo- and thermo-responsive polymer He joined Peter Diner’s group at the Royal Institute of Technology in 2017 as Ph.D. student and his research revolves around organic azides, developing methodologies for their reduction or exploiting the unique reactivity of perfluorinated aromatic azides in a photo-promoted synthesis of optical active sulfonimidamides and their applications in materials. Feature formed amines were either Boc-protected to carbamates or further reacted with an epoxide to yield -amino alcohols (Scheme 3).[29]
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