CS676 Real Time Systems: Magnus Technology R&amp;D Real Time Systems

Nielsen, Roy S.

doi:10.2172/1183952

Cited by 1 publication

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“…The heterocyclic ring is generally prepared by cyclocarbonylation of o -aminophenols with phosgene , or other carbonyl group donors, such as molten urea, ,,,, triphosgene, ,,,, aryl chloroformates, , carbonyl diimidazole, ,,,, etc. − Carbon monoxide has also been used for oxidative and reductive cyclocarbonylations of o -aminophenols and o -nitrophenols, respectively. Some examples of cyclization of o -hydroxyaryl isocyanates, generated in situ by Curtius, Schimdt, Hoffmann, , and Lossen , rearrangements of suitable salicylic acid derivatives, are also known. However, all of the aforesaid methods suffer from various drawbacks, such as air sensitivity of o -aminophenols, toxicity of phosgene, hazardous mixtures of CO and O 2 used in oxidative cyclocarbonylation, high temperatures and pressures, and undesirable side products.…”

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confidence: 99%

Synthesis of 3-Alkylbenzoxazolones fromN-Alkyl-N-arylhydroxylamines by ContiguousO-Trichloroacetylation, Trichloroacetoxyortho-Shift, and Cyclization Sequence

Ram

Soni

2013

J. Org. Chem.

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Benzoxazolone pharmacophore is present in clinical pharmaceuticals, drug candidates, and many compounds having a wide spectrum of biological activities. The methods available for the synthesis of benzoxazolones have limited diversity due to problems in accessibility and air-sensitivity of diversely substituted o-aminophenols from which they are generally prepared by cyclocarbonylation with phosgene or its equivalents. The present paper describes a mild method for the synthesis of 3-alkylbenzoxazolones from easily accessible and air-stable nitroarenes. Nitroarenes were converted to N-alkyl-N-arylhydroxylamines in two steps involving partial reduction to arylhydroxylamines followed by selective N-alkylation. Treatment of N-alkyl-N-arylhydroxylamines with trichloroacetyl chloride and triethylamine afforded 3-alkylbenzoxazolones generally in good yields through an uninterrupted three-step sequence involving O-trichloroacetylation, N→C(ortho) trichloroacetoxy shift, and cyclization in a single pot at ambient temperatures. The present method is mild, wide in scope, economical, and regioselective. Many sensitive groups like alkyl and aryl esters, amide, cyano, and the carbon-carbon double bond survive the reaction.

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