DTBP‐Mediated Cascade Spirocyclization and Dearomatization of Biaryl Ynones: Facile Access to Spiro[5.5]trienones through C(sp³)−H Bond Functionalization

Abstract

Oxidative radical cascade spirocyclization and dearomatization of biary ynones with a variety of hydrocarbons including toluenes, ethers, ketones, and alkanes has been developed to construct alkyl substituted spiro[5.5]trienones.

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

“…1 b ,12 It is noteworthy to mention that to date there is no report on the ipso -annulation of biaryl ynones using carbonylated-alkyl radicals, although a few other carbo-functionalizations have recently become available. 13 As shown in Scheme 3, the reaction of biaryl ynone 4a (see Fig. S2 for their structures in the ESI†) with diketone 2a proceeded smoothly to furnish the desired spiro[5.5]enone 5a in 89% yield.…”

C-centered radical-initiated cyclization by directed C(sp3)–H oxidative functionalization

“…In a variation of the processes, Meng, Si, and Yang's group subsequently showed that the methoxy group could also be utilized as a leaving group to promote this transformation (Scheme 49). 96 Moreover, this transformation featured a broad substrate scope and green reaction conditions, in which no metal and base were required.…”

“…Intermediate 167 was furnished through coupling of t-BuO In a variation of the processes, Meng, Si, and Yang's group subsequently showed that the methoxy group could also be utilized as a leaving group to promote this transformation (Scheme 49). 96 Moreover, this transformation featured a broad substrate scope and green reaction conditions, in which no metal and base were required. Shen and Gao's group was intrigued by the α-C(sp 3 )-H bond functionalization of simple ketones or acetonitrile and their subsequent participation in 5-exo-trigcyclization with an -SMe moiety.…”

Divergent Construction of Thiochromanes and N-Arylbutanamides via Arylthiodifluoromethyl Radical-Triggered Cascade of Alkenes

“…Despite their potential benefits, these approaches for the synthesis of thiochromanes suffer from some limitations including the inability to assemble fluorine-containing thiochromanes, complex substrates, metal catalysts, and additional additives. Driven by the potential pharmacological utilization of fluorine-containing building blocks, the ongoing development of synthesis methodology for thiochromanes, and our interests in cascade reactions, − we here report for the first time a radical cyclization of alkenes with arylthio-difluoroacetic acid for the synthesis of difluoromethylated thiochromanes through silver-catalyzed decarboxylative difluoroalkylation-carbocyclization reaction (Path A, Scheme d). To our delight, a selective strategy for the synthesis of 2,2-disubstituted- N -arylbutanamides derivatives was also achieved when changing an alkene from inactive alkene 1-phenylpent-4-en-1-one to N -phenyl- N -tosylmethacrylamide (Path B, Scheme d).…”