Development of a [2 + 2]-Nitroso/Alkene Cycloaddition Using Sodium Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate
Jia-Xuan Chen1, Prakash D Jadhav1, Ching-Nung Chen1
1Frontier Research Center of Matter Science and Technology, Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan 30013, Republic of China.
Abstract:
Sodium tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate (NaBArF) catalyzes the [2 + 2] cycloaddition of 1,4-disubstituted cyclopenta-1,3-dien-2-yl esters with nitrsobenzene in toluene, affording two isolable regioisomers of 6-oxa-7-azabicyclo[3.2.0] heptanes, which thermally rearrange into the same 4-aminocyclopent-1-en-3-ones. In the case of 4-substituted cyclopenta-1,3-dien-2-yl esters, their initial [2 + 2] cycloaddition intermediates undergo a rapid ring expansion to afford six-membered piperidone derivatives efficiently.
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