Expeditious Access to Spiro-Fused 2,5-Cyclohexadienones via Thio(seleno)cyanative ipso-Cyclization

Abstract

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.

Copper(ii)-catalyzed oxidative ipso-annulation of N-arylpropiolamides and biaryl ynones with 1,3-diketones: construction of diketoalkyl spiro-trienones

“…In recent years, dearomative ipso -cyclization of N -arylpropiolamides induced by electrophilic or radical reagents has proved to be an efficient and attractive strategy for the construction of spiro[4.5]trienones. 5 These spirocyclizations either relied on heteroatom (S, Se, N, P, Si, I, Br, Cl, and F) functionalization via C–X bond formation 6 or carbo-functionalization involving C–C bond formation, 7–9 on the alkyne. Among the carbo-functionalized ipso -annulations of N -arylpropiolamides, the majority of the methods investigated are either arylated or acylated cyclizations promoted by the respective carbon-centered aryl or acyl (sp 2 -carbon) radicals generated from diverse sources.…”

Nitro-Spirocyclization of Biaryl Ynones with tert-Butyl Nitrite: Access to NO2-Substituted Spiro[5,5]trienones

“…Consequently, several efficient oxidative/nucleophilic/electrophilic dearomatization and transition-metal or radical-promoted dearomatization processes have been accomplished by many groups so far. − As known, the radical cascade 5- exo -trig and 6- exo -trig spirocyclization of alkynes to access spirocycles have become active areas of research recently. − ,, Among them, many groups respectively developed excellent strategies for the synthesis of spiro­[5,5]­trienones by using biaryl ynones as the starting materials. ,, Recently, our group reported a photoinduced spirocyclization reaction to give SCN-featured spiro­[5,5]­trienones . Despite this advanced work, there is still a fundamental need to find some easy operations and good regioselectivity systems to gain spiro­[5,5]­trienones.…”

ipso-Cyclization of unactivated biaryl ynones leading to thio-functionalized spirocyclic enones

“…9 In view of the importance of organosulfur molecules, efficient methods for the construction of C–S bonds have received significant attention from organic chemists. 10 In continuation of our ongoing work on the development of oxidative dearomatization reactions of alkyne tethered aromatic compounds, 11 herein, we reveal CAN-mediated ipso -annulation of unactivated biaryl ynones with S -centered radicals (SCN and SCF 3 ), providing ready access to the corresponding thio-functionalized spirocyclic enones (Scheme 1d).…”