New Catalytic Liquid-Phase Ammoxidation Approach to the Preparation of Niacin (Vitamin B₃)

Abstract

New highly dispersed bimetallic nanoscale catalysts based on rhenium combined with antimony or bismuth have been shown to be highly effective for the ammoxidation of 3-picoline to nicotinonitrile (precursor for vitamin B3) under mild conditions in the liquid phase.

Heterometallic Complexes with Rhenium- and Iron-Bismuth Bonds

“…In case of hexafluoroiso-propyl residues, alcohol eliminations involving the Cp rings were suppressed [10]. 2 in the same solvent at ambient temperature. A slow color change from yellow to orange and finally to dark green was observed (Scheme 3).…”

“…Compared to Re-Bi compounds [2, 13, 17 -19], more literature is available on complexes containing Fe-Bi bonds [20,21]. The focus of our work was again on bismuthanes bearing a bismuth atom connected to organoiron fragments, such as η 5 -cyclopentadienyl dicarbonyl iron [Cp(CO) 2 perature for a period of 72 h resulted in a bright-orange suspension, which was concentrated to one third of the volume. Subsequent filtration provided 5 in form of a crude yellow powder in an excellent yield of 89 %.…”

“…Monitoring the reaction by NMR provided evidence for the occurrence of two intermediates, which we assigned as [Cp 2 ReBi(O t Bu) 2 ], 1, and [(Cp 2 Re) 2 Bi(O t Bu)], 2, but these compounds eluded isolation due to fast subsequent reactions [13]. Analogs of 1, [Cp 2 Re-BiR 2 ], could be prepared for R = OCH(CF 3 ) 2 , I, and R=o-tol, II, as the electron-withdrawing alkoxide ligands slow down further reactions and as Bi-C bonds are relatively inert, respectively. Here we report how we got access to 1 itself by modifying the reaction conditions, and to an analog of 2 with a hexafluoro isopropyl residue.…”

Predictive design of engineered multifunctional solid catalysts

“…45 The need to adeptly design specific active sites is already wellestablished within nanoparticle chemistry; where intrinsic compositional control at the nanoscale coupled with tuning the size-and shape-of the metal nanoparticles, ensues the origin of discrete single-sites that are catalytically active and selective (see Table 3). [50][51][52] A wide-range of synthetic strategies 53 have been recently evolved to generate metal nanoparticles with innate control on morphology and particle size. One such method involves the introduction of carbonyl-capped metalnanoclusters to solid (typically siliceous) supports to form particles of specific sizes and molecularity.…”

Probing the origin of in situ generated nanoparticles as sustainable oxidation catalysts

“…It is well known 22 that nanoparticle size and degree of siteisolation are crucial factors that lead to the generation of single-30 sites that are responsible for boosting the overall catalytic efficiency in nanoparticle-based catalysts that were previously studied 23 for catalytic oxidations and hydrogenations. 24 Whilst 35 these studies focussed on using cluster-based precursors for generating nanoparticles (by post-synthesis deposition or grafting on mesoporous supports), this novel approach illustrates a "onepot" in situ method for achieving isolated active sites in porous chloropyrophosphate-based framework architectures; where the 40 inherent nature of the framework can be advantageously tailored for efficient shape-selective catalytic oxidations using molecular oxygen. Stringent recycle tests show that these materials can be ffectively reused as heterogeneous catalysts for a minimum of 45 three cycles, with little to no drop in performance or selectivity.…”