Here, we report the first study to use Fe 2 S 2 (CO) 6 as a well-defined petroleum-soluble precatalyst for partial hydrogenation of polycyclic aromatic and heteroaromatic compounds, including pyrene, phenanthrene, naphthalene, and benzothiophene. The in situ-generated heterogeneous catalyst was characterized using a combination of thermogravimetric analysis (TGA), combustion analysis (CHNS), Fourier transform infrared (FT-IR) spectroscopy, scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy-energy dispersive Xray (SEM-EDX). Catalytic performance of Fe 2 S 2 (CO) 6 was evaluated in a batch microreactor coupled with an agitator, varying reaction temperature, pressure, and precatalyst loading. The active phase, consisting of iron sulfide nanoparticles, was prepared from purified Fe 2 S 2 (CO) 6 in toluene; no sulfur additive is required. The results demonstrate that a "presulfided" iron catalyst leads to partial hydrogenation of polycondensed aromatics under moderate conditions, with naphthalene showing only low conversion. Activated carbon, γ-alumina, and activated silica are all effective dispersants for the Fe precursor. The reactivity shows self-consistent substrate dependence, varying with the resonance energy stabilization of the starting compounds and partially saturated intermediates coupled with the surface adsorption enthalpy of the aromatic ring system. The active catalyst derived from this precursor exhibits higher catalytic activity than commercial iron sulfide precatalysts. Importantly, the catalyst is active for hydrodesulfurization (HDS) of benzothiophene, albeit modestly so.

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Catalytic iodine in the presence of water acts indirectly as a source of Brønsted acid and, concurrently, generates iodonium ion and hydrogen peroxide, which mediate the final oxidative aromatization step in the multicomponent cyclocondensation of an aromatic amine and two aliphatic aldehyde compounds. The oxidative cycle in this and related iodine‐catalyzed reactions is seldom discussed, generally unoptimized, and rarely investigated in detail. This work establishes that two independent catalytic cycles (H+ and I−/I+) drive such multicomponent cyclocondensation/ oxidation reactions, provided that the oxidant is generated in sufficient concentration to inhibit oxidation of the dihydroquinoline by the intermediate iminium cation. The complementary dual catalytic cycles, when optimized, act in concert to suppress side product formation, which simplifies isolation and purification of the self‐aggregating products, and increases the efficiency and scope of the Wang‐Kozlov multicomponent reaction.

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