Synthesis of polychloromethylated and halogenated spiro[5,5]trienones via dearomative spirocyclization of biaryl ynones

Abstract

We disclosed a selective polychloromethylation and halogenation reaction of alkynes via a radical addition/spirocyclization cascade sequence, in which applying polyhaloalkanes as the precursor of polyhalomethyl and halogen radical. Across this...

Metal-free polychloromethylation/cyclization of unactivated alkenes towards ring-fused tricyclic indolones and benzoimidazoles

“…Based on the experimental results and previous reports, 11,13 a possible mechanism is proposed in Scheme 4. Initially, under heating, the thermal homolytic cleavage of DTBP gives a tert -butoxy radical to initiate the radical cascade.…”

“…Dichloromethane and chloroform are common feedstocks in organic laboratories and are frequently used as solvents in many reactions. Besides, dichloromethane and chloroform can also be used as ideal di- and trichloromethyl radical precursors to construct various polychloromethylated structures via a hydrogen atom transfer 11 or halogen atom transfer process. 12 Our group has also made contributions to the radical polychloromethylation of alkenes toward complex di- and trichloromethylated structures especially heterocyclic structures.…”

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

“…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). For example, Chen and Zhou reported an iron-catalyzed cascade silyl radical addition/6- exo -trig cyclization/dearomatization of biaryl ynones with silane, affording silylated spiro[5.5]trienones in good yields [ 35 ].…”

“…For example, Chen and Zhou reported an iron-catalyzed cascade silyl radical addition/6- exo -trig cyclization/dearomatization of biaryl ynones with silane, affording silylated spiro[5.5]trienones in good yields [ 35 ]. In addition, several groups have demonstrated some elegant examples based on C-, N-, P-, S-, Si-, Se-centered radicals-induced cascade cyclization of biaryl ynones in the presence of transition-metal catalysts, oxidants or photocatalysts [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. For example, Duan and Yang reported the preparation of alkyl-functional spiro[5.5]trienone through alkylative dearomatization and the spirocyclization of biaryl ynones, respectively [ 29 , 33 ].…”

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).…”