Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes

Nitrene-transfer from azides to isocyanides: Unveiling its versatility as a promising building block for the synthesis of bioactive heterocycles

Cross-coupling azide and isocyanide have recently gained recognition as ideal methods for efficiently synthesizing asymmetric carbodiimides. This reaction exhibits high reaction rates, efficiency, and favorable atom/step/redox economy. It enables the nitrene-transfer process, facilitating the formation of C-N bonds and providing a direct and cost-effective synthetic strategy for generating diverse carbodiimides. These carbodiimides are highly reactive compounds that can undergo in-situ transformations into various functional groups and organic compounds, including heterocycles. Developing one-pot and tandem processes in this field has significantly contributed to advancements in organic chemistry. Moreover, the demonstrated utility of these architectural motifs extends to areas such as chemical biology and medicinal chemistry, further highlighting their potential in various scientific applications.

Aziridination Reactivity of a Manganese(II) Complex with a Bulky Chelating Bis(Alkoxide) Ligand

Treatment of Mn(N(SiMe₃)₂)₂(THF)₂ with bulky chelating bis(alkoxide) ligand [1,1′:4′,1′′-terphenyl]-2,2′′-diylbis(diphenylmethanol) (H₂[O-terphenyl-O]^Ph) formed a seesaw manganese(II) complex Mn[O-terphenyl-O]^Ph(THF)₂, characterized by structural, spectroscopic, magnetic, and analytical methods. The reactivity of Mn[O-terphenyl-O]^Ph(THF)₂ with various nitrene precursors was investigated. No reaction was observed between Mn[O-terphenyl-O]^Ph(THF)₂ and aryl azides. In contrast, the treatment of Mn[O-terphenyl-O]^Ph(THF)₂ with iminoiodinane PhINTs (Ts = p-toluenesulfonyl) was consistent with the formation of a metal-nitrene complex. In the presence of styrene, the reaction led to the formation of aziridine. Combining varying ratios of styrene and PhINTs in different solvents with 10 mol% of Mn[O-terphenyl-O]^Ph(THF)₂ at room temperature produced 2-phenylaziridine in up to a 79% yield. Exploration of the reactivity of Mn[O-terphenyl-O]^Ph(THF)₂ with various olefins revealed (1) moderate aziridination yields for p-substituted styrenes, irrespective of the electronic nature of the substituent; (2) moderate yield for 1,1′-disubstituted α-methylstyrene; (3) no aziridination for aliphatic α-olefins; (4) complex product mixtures for the β-substituted styrenes. DFT calculations suggest that iminoiodinane is oxidatively added upon binding to Mn, and the resulting formal imido intermediate has a high-spin Mn(III) center antiferromagnetically coupled to an imidyl radical. This imidyl radical reacts with styrene to form a sextet intermediate that readily reductively eliminates the formation of a sextet Mn(II) aziridine complex.

Transition metal-catalysed carbene- and nitrene transfer to carbon monoxide and isocyanides

Transition metal-catalysed carbene- and nitrene transfer to the C1-building blocks carbon monoxide and isocyanides provides heteroallenes (i.e. ketenes, isocyanates, ketenimines and carbodiimides). These are versatile and reactive compounds allowing in situ transformation towards numerous functional groups and organic compounds, including heterocycles. Both one-pot and tandem processes have been developed providing valuable synthetic methods for the organic chemistry toolbox. This review discusses all known transition metal-catalysed carbene- and nitrene transfer reactions towards carbon monoxide and isocyanides and in situ transformation of the heteroallenes hereby obtained, with a special focus on the general mechanistic considerations.

Synthesis and structure of a new bulky bis-(alkoxide) ligand on a terphenyl platform

A new sterically bulky chelating bis-(alkoxide) ligand 3,3'-([1,1':4',1''-terphen-yl]-2,2''-di-yl)bis-(2,2,4,4-tetra-methyl-pentan-3-ol), (H2[OO]tBu), was prepared in a two-step process as the di-chloro-methane monosolvate, C36H50O2·CH2Cl2. The first step is a Suzuki-Miyaura coupling reaction between 2-bromo-phenyl-boronic acid and 1,4-di-iodo-benzene. The resulting 2,2''-di-bromo-1,1':4',1''-terphenyl was reacted with t BuLi and hexa-methyl-acetone to obtain the desired product. The crystal structure of H2[OO]tBu revealed an anti conformation of the [CPh2(OH)] fragments relative to the central phenyl. Furthermore, the hydroxyl groups point away from each other. Likely because of this anti-anti conformation, the attempts to synthesize first-row transition-metal complexes with H2[OO]tBu were not successful.

Catalytic synthesis of azoarenes via metal-mediated nitrene coupling

Various valuable properties of azoarenes (“azo dyes”), including their vivid colors and their facile cis-trans photoisomerization, lead to their wide use in the chemical industry. As a result, ~700,000 metric...