• Journal of Radiopharmaceuticals and Molecular Probes
• /
• v.4 no.1
• /
• pp.16-21
• /
• 2018

Organoboron compounds and their derivatives are synthetically versatile building blocks because they are readily available, stable, and highly useful for potential organic transformations. Arylboronic esters are of particular interest due to their well-established synthetic methods: transition metal catalyzed borylations of aryl halides. However, the use of aryl halides as an electrophile has one serious disadvantage: formation of toxic halogenated byproducts. A promising alternative substrate to aryl halides would be phenol derivatives such as aryl ethers, esters, carbamates and sulfonates. The phenol derivatives involve several advantages: their abundance, relatively low toxicity and versatile synthetic application. However, utilization of the aryl methyl ether, which is one of the simplest phenol derivatives, remains as a challenge, as C-OMe bond activation requires high activation energy and methoxides are not good leaving groups. Nevertheless, there have been a significant recent progress on ipso-borylation of aryl methyl ether including Martin's nickel catalysis. Here, we review the current advance on the borylation of carbon-oxygen bonds of unactivated C-OMe bond in aromatic compounds.

• Journal of the Korean Chemical Society
• /
• v.60 no.4
• /
• pp.251-256
• /
• 2016

This paper describes the synthesis of alkali metal salts of urea (ureates) and their application to the direct preparation of 4-nitrosoaniline from nitrobenzene via nucleophilic aromatic substitution of hydrogen. Sodium and potassium ureates were readily prepared from the reaction of urea with sodium hydride, metal methoxides, and metal hydroxides. The effect of ureates as nucleophiles on the conversion of nitrobenzene to 4-nitrosoaniline was investigated and compared with that of a urea-metal hydroxide mixture. It was found that the ureates were superior for producing 4-nitrosoaniline owing to their higher thermal stability of the ureate. The ureate obtained from the treatment of urea with sodium hydride gave the highest yield for the preparation of 4-nitrosoaniline. The ureates generated from the reaction of urea with metal hydroxide also gave high yields of 4-nitrosoaniline. Catalytic hydrogenation of 4-nitrosoaniline afforded polymer-grade 1,4-benzenediamine in quantitative yield.

• Journal of the Korean Chemical Society
• /
• v.31 no.1
• /
• pp.79-83
• /
• 1987

Trimethyl-and triphenyl-metal (IVA) methoxides were reacted with phenylisocyanate at various temperatures. Even at 100$^{\circ}C$, methyltrimethylsilyl ether, methyltriphenylsilyl ether and triphenyltin methoxide produced the cyclic dimer of phenylisocyanate, N,N'-diphenyluretidine-2,4-dione. But the other compounds produced only the cyclic trimer of phenylisocyanate, phenylisocyanurate. And above 200$^{\circ}C$, considerable amounts of diphenylcarbodiimide was formed by all the organometallic compounds. From these results, the mechanism of cyclic polymerization of phenylisocyanate by the organometal catalysts, and the correlation of substituents with the reactivity were discussed.