1,2,4-Oxadiazoles from cycloreversions of oxadiazabicyclo[3.2.0]heptenes: 1-azetines as thiocyanate equivalents
摘要:
1,3-Dipolar cycloaddition of nitrile oxides to 4-aryl-2-alkylthio-1-azetines gave a series of oxadiazabicyclo[3.2.0]heptenes as single diastereoisomers. Heating these cycloadducts in toluene resulted in an overall [2+2]-cycloreversion to give 5-alkylthio-3-aryl-1,2,4-oxadiazoles. In this process, the 1-azetine behaves as a thiocyanate equivalent. When the nitrile oxide substituent was 2-azidobenzene, the azide could be converted into a 1,2,3-triazole giving a (1,2,4-oxadiazolo)-(1,2,3-triazolo)-1,2-disubstituted benzene. 1,2,4-Oxadiazoles are sought after in medicinal chemistry and materials sciences. (c) 2012 Elsevier Ltd. All rights reserved.
Pyridines from Azabicyclo[3.2.0]hept-2-en-4-ones through a Proposed Azacyclopentadienone
作者:Karl Hemming、Musharraf N. Khan、Vishnu V. R. Kondakal、Arnaud Pitard、M. Ilyas Qamar、Craig R. Rice
DOI:10.1021/ol202924s
日期:2012.1.6
Pyridines have been formed by heating azabicyclo[3.2.0]hept-2-en-4-ones in toluene. The generation of a 3-azacyclopentadienone intermediate via a [2 + 2]-cycloreversion Is proposed as the key step. A Diels-Alder reaction of a styrene, extrusion of carbon monoxide, and loss of hydrogen then gives the pyridine. The process parallels the well-known synthesis of benzenes from cyclopentadienones. The azabicyclo[3.2.0]hept-2-en-4-ones were synthesized from the reaction between readily available cyclopropenones and 1-azetines, In which the cyclopropenones behave as all-carbon 1,3-dipolar equivalents.
1,2,4-Oxadiazoles from cycloreversions of oxadiazabicyclo[3.2.0]heptenes: 1-azetines as thiocyanate equivalents
作者:Karl Hemming、Musharraf N. Khan、Paul A. O'Gorman、Arnaud Pitard
DOI:10.1016/j.tet.2012.12.007
日期:2013.1
1,3-Dipolar cycloaddition of nitrile oxides to 4-aryl-2-alkylthio-1-azetines gave a series of oxadiazabicyclo[3.2.0]heptenes as single diastereoisomers. Heating these cycloadducts in toluene resulted in an overall [2+2]-cycloreversion to give 5-alkylthio-3-aryl-1,2,4-oxadiazoles. In this process, the 1-azetine behaves as a thiocyanate equivalent. When the nitrile oxide substituent was 2-azidobenzene, the azide could be converted into a 1,2,3-triazole giving a (1,2,4-oxadiazolo)-(1,2,3-triazolo)-1,2-disubstituted benzene. 1,2,4-Oxadiazoles are sought after in medicinal chemistry and materials sciences. (c) 2012 Elsevier Ltd. All rights reserved.