Synthesis of 3-Alkylbenzoxazolones from N-Alkyl-N-arylhydroxylamines by Contiguous O-Trichloroacetylation, Trichloroacetoxy ortho-Shift, and Cyclization Sequence
摘要:
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.
Palladium-Catalyzed Dehydrative Cross-Coupling of Allylic Alcohols and <i>N</i>-Heterocycles Promoted by a Bicyclic Bridgehead Phosphoramidite Ligand and an Acid Additive
作者:Kyungjun Kang、Jaewook Kim、Ansoo Lee、Woo Youn Kim、Hyunwoo Kim
DOI:10.1021/acs.orglett.6b00001
日期:2016.2.5
A mild and efficient dehydrative cross-coupling reaction between allylic alcohols and N-heterocycles using palladium catalysis is reported. A bicyclic bridgehead phosphoramidite (briphos) ligand together with Pd(dba)2 is a highly efficient catalyst, and an acid additive involved in the rate-determining step promotes the catalytic cycle. The coupling reaction of allylic alcohols with N-heterocycles
The Reaction of Dialkyl Carbonates with<i>o</i>-Aminophenol Catalysed by K<sub>2</sub>CO<sub>3</sub>: A Novel High-Yield Synthesis of<i>N</i>-Alkylbenzoxazol-2-ones
作者:Maurizio Selva
DOI:10.1055/s-2003-42464
日期:——
At 130-150 °C and in the presence of catalytic K2CO3, o-aminophenol (1) readily reacts with dialkyl carbonates (2: ROCO2R; 2a: R = Me, 2b: Et, 2c: Allyl, 2d: Bn) to give the corresponding N-alkylbenzoxazol-2-ones (3a-d) in high yields (88-98%). This reaction is a rare example where dialkyl carbonates may simultaneously act as carbonylating and alkylating agents likely through a BAc2/BAl2 sequence. Moreover, compounds 2a-c serve also as solvents. In the case of 2d, 1,2-dimethoxyethane (DME) is the reaction medium.
Photochemical rearrangements of 1,2-benzisoxazolinones
作者:Thomas H. Kinstle、Larry J. Darlage、C. L. McIntosh
DOI:10.1021/jo00807a017
日期:1971.4
Synthesis of 3-Alkylbenzoxazolones from <i>N</i>-Alkyl-<i>N</i>-arylhydroxylamines by Contiguous <i>O</i>-Trichloroacetylation, Trichloroacetoxy <i>ortho</i>-Shift, and Cyclization Sequence
作者:Ram N. Ram、Vineet Kumar Soni
DOI:10.1021/jo401985h
日期:2013.12.6
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.
Asymmetric Dearomatization of Phenols via Ligand‐Enabled Cooperative Gold Catalysis
作者:Yongliang Zhang、Ke Zhao、Xinyi Li、Carlos D. Quintanilla、Liming Zhang
DOI:10.1002/anie.202309256
日期:2023.9.18
Asymmetric dearomatization of phenols was achieved by employing chiral bifunctional phosphine ligands in cooperative goldcatalysis. This transformation demonstrated a remarkable generality, affording the desired product with high yields (up to 99 %) and excellent enantioselectivities (ee up to 99 %).