Oxidative Cyclization of Aryl Ynones with NaNO₂ for the Divergent Synthesis of NO₂‐Containing Spiro[5.5]trienones, Indenones and Thioflavones

Abstract

A K 2 S 2 O 8 -promoted nitration/spirocyclization of biaryl ynones using inexpensive NaNO 2 as nitro source has been described. This cascade reaction is triggered by nitration of alkyne and followed by 6-exo-trig spirocyclization, dearomatization, forming the NO 2 -containing spiro[5.5]trienones in 63-85% yields. The present reaction also provides a practical method for the synthesis of nitrated indenones and thioflavones with 58-85% yields.

Progress in the Construction of Spirocyclohexadienones via Alkyne-Involving Dearomatization

“…2022 年, 陈斐、周能能等 [53] 报道了一例铁催化的硅烷化 去芳构化反应, 硅烷被攫氢后得到硅中心自由基, 自由 基进攻炔酮, 最终实现了一系列硅基化螺 [5,5]三烯酮衍 生物的合成(Scheme 20b). 同年, 杨文超等 [54] 报道了一 种合成硝基螺 [5,5]三烯酮衍生物的方法, 在 K 2 S 2 O 8 存 在下, 亚硝酸钠被活化产生硝基自由基(Scheme 20c). 2023 年, 李泽江等 [55] 报道了一例亚硝酸叔丁酯(TBN)参 与的联芳基炔酮硝基化去芳构化反应, 同样实现了一系 列硝基螺 [5,5]三烯酮衍生物的合成(Scheme 20d).…”

Synthesis of Indenones via Persulfate Promoted Radical Alkylation/Cyclization of Biaryl Ynones with 1,4-Dihydropyridines

“…In addition, radical cascade reactions involving the 1,2-difunctionalization of alkyne have become a versatile tool in contemporary organic chemistry [ 11 , 12 , 13 , 14 ]. To date, the cyclization of alkynes toward the synthesis of cyclic compounds has been effectively investigated [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Recently, the radical cascade cyclization of biaryl ynones has been demonstrated to be a useful approach to construct six-membered spiro[5,5]trienones [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ] with the development of different types of radical precursors ( Scheme 1 a–c).…”

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).…”