Directed ortho-metalation versus reductive amination in the preparation of polytopic, highly substituted, and sterically congested amine-S-arylthiocarbamates as thiophenol precursors

The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update

The aryl O-carbamate (ArOAm) group is among the strongest of the directed metalation groups (DMGs) in directed ortho metalation (DoM) chemistry, especially in the form Ar-OCONEt2. Since the last comprehensive review of metalation chemistry involving ArOAms (published more than 30 years ago), the field has expanded significantly. For example, it now encompasses new substrates, solvent systems, and metalating agents, while conditions have been developed enabling metalation of ArOAm to be conducted in a green and sustainable manner. The ArOAm group has also proven to be effective in the anionic ortho-Fries (AoF) rearrangement, Directed remote metalation (DreM), iterative DoM sequences, and DoM-halogen dance (HalD) synthetic strategies and has been transformed into a diverse range of functionalities and coupled with various groups through a range of cross-coupling (CC) strategies. Of ultimate value, the ArOAm group has demonstrated utility in the synthesis of a diverse range of bioactive and polycyclic aromatic compounds for various applications.

DABCO-Catalyzed Reaction of 2-Naphthols with Aryl Isothiocyanates: Access to 2-Iminonaphtho-1,3-oxathioles

2-Naphthols 1 were found to react with aryl isothiocyanates 2 to provide 2-iminonaphtho-1,3-oxathioles 3 in the presence of DABCO as a catalyst. When elemental sulfur was used, moderate to good yields of 3 could be achieved from a nearly equimolar mixture of two starting materials 1 and 2. Products 3 could also be formed in the absence of sulfur or an external oxidant. In the latter case, an additional equivalent of 2 was found to act as a dehydrogenating agent.

Conformational Effects of [Ni2 (μ-ArS)2 ] Cores on Their Electrocatalytic Activity

Two nickel complexes supported by tridentate NS₂ ligands, [Ni₂ (κ-N,S,S,S'-N^Ph {CH₂ (MeC₆ H₂ R')S}₂ )₂ ] (1; R'=3,5-(CF₃ )₂ C₆ H₃ ) and [Ni₂ (κ-N,S,S,S'-N^iBu {CH₂ C₆ H₄ S}₂ )₂ ] (2), were prepared as bioinspired models of the active site of [NiFe] hydrogenases. The solid-state structure of 1 reveals that the [Ni₂ (μ-ArS)₂ ] core is bent, with the planes of the nickel centers at a hinge angle of 81.3(5)°, whereas 2 shows a coplanar arrangement between both nickel(II) ions in the dimeric structure. Complex 1 electrocatalyzes proton reduction from CF₃ COOH at -1.93 (overpotential of 1.04 V, with i_cat /i_p ≈21.8) and -1.47 V (overpotential of 580 mV, with i_cat /i_p ≈5.9) versus the ferrocene/ferrocenium redox couple. The electrochemical behavior of 1 relative to that of 2 may be related to the bent [Ni₂ (μ-ArS)₂ ] core, which allows proximity of the two Ni⋅⋅⋅Ni centers at 2.730(8) Å; thus possibly favoring H⁺ reduction. In contrast, the planar [Ni₂ (μ-ArS)₂ ] core of 2 results in a Ni⋅⋅⋅Ni distance of 3.364(4) Å and is unstable in the presence of acid.

Easily reduced bis-pincer (NS2)2molybdenum(iv) to (NHS2)2Mo(ii) by alcohols vs. redox-inert (NS2)(NHS2)iron(iii) complexes

Iron and molybdenum complexes supported by a pincer-type dianionic [NS₂]²⁻ donor were prepared to compare their structural, spectroscopic, and electrochemical properties.

Redox flexibility of iron complexes supported by sulfur-based tris(o-methylenethiophenolato)amine relative to its tripodal oxygen-based congener

Tripodal ligands designed to generate a local C₃ symmetry have resulted in novel types of metal complexes that feature unusual bonding and electronic properties.