A facile oxidative dearomatization of N-(pmethoxyaryl)propiolamides has been established for the synthesis of spiro-fused 2,5-cyclohexadienone frameworks via thio(seleno)cyanative ipso-cyclization in the presence of ceric ammonium nitrate (CAN) as the oxidant. The present method, involving the formation of C−S and C−C bonds, was also extended to (pmethoxyaryl)propiolates for thiocyanative ipso-cyclization. Furthermore, the obtained chalcogeno-spirocyclohexadienones were transformed into uniquely functionalized spirocyclohexadienone derivatives.
A variety of acrylamides holding an unactivated N-benzyl group underwent dearomative ipso-cyclization
induced by sulfur-centered radicals (SCN/ SCF3/ SO2Ar) in the presence of ceric ammonium nitrate (CAN) as the
oxidant to furnish azaspirocycles in good yields. This is the first
report on ipso-dearomatization of N-benzyl acrylamides that proceeds without a substituent at the para-position of the aromatic ring. The developed conditions
are also found to be suitable for substrates holding substituents
such as F, NO2, OMe, OH, and OAc at the para-position. The reaction features water as the source of oxygen, is
compatible with a variety of functional groups, and proceeds in a
short time.
An unprecedented copper-catalyzed ipso-annulation reaction of N-(p-methoxyaryl)propiolamides with 1,3-diketones has been developed, which enables the assembly of diketo-alkylated spiro[4.5]trienones involving oxidative dearomatization in the presence of ammonium persulfate [(NH4)2S2O8] as...
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