Electrooxidative dearomatization of biaryls: synthesis of tri- and difluoromethylated spiro[5.5]trienones

Abstract

Radical spirocyclization via dearomatization has emerged as an attractive strategy for the rapid synthesis of structurally diverse spiro molecules. We report the use of electrochemistry to perform an oxidative dearomatization...

Empowering Visible Light Catalysis: Brominative Dearomatizationof Biaryl Ynones

“…Treatment of 2a with MeMgCl at ice cold condition afforded the 1,2-carbonyl addition product I in 76% yield. 16 The selective reduction of 2a under Luche conditions gave II in 92% yield. The 3 '-bromo-2'-phenyl-4'H-spiro[cyclohexa[2,5]diene-1,1'-naphthalene]-4,4'-dione 2a can be converted to 3 '-bromo-4-methylene-2'-phenyl-4'H-spiro[cyclohexa[2,5]diene-1,1'-naphthalen]-4'-one moiety III by treatment with CH3PPh3Br (2.5 equiv.)…”

“…and t BuOK in THF solvent. 16 A hexahydro spiro-cyclization product IV can be encountered followed by hydrogenation in presence of 10% Pd(C) and MeOH solvent in 1atm H2 atmosphere. Epoxidation of 2a to the tetra-substituted double bond have been performed using H2O2 and Na2CO3 in EtOH solvent at room temperature (V, 60%).…”

“…Epoxidation of 2a to the tetra-substituted double bond have been performed using H2O2 and Na2CO3 in EtOH solvent at room temperature (V, 60%). 16 Next, to emphasize the presence of halo-group in spiro-product, the Suzuki-Miyaura cross coupling reaction of (2a) and 2-bromophenylboronic acid followed by the Pd-catalyzed intra-molecular cyclization, gave 14H-spiro[benzo[f]tetraphene-9,1'-cyclohexa[2,5]diene]-4',14-dione VI as a sole product (Scheme 9). 26 Finally,[2][3][4]5]diene-1,9 '-naphtho[2,3b]thiophene]-4,4'-dione was synthesized from 2v following the procedure mentioned in the ref.…”

“…15 Recently, Ackermann group and Reddy group have developed electrooxidative dearomatization of biaryl ynones to construct di-and tri-fluoromethylated spiro[5.5]trieneones and selenylated dibenzocycloheptenones and spiro[5.5]trieneones respectively. 16,17 Though all of these methods elegantly provide diversely substituted spiro[5.5]trieneones, they necessitate the use of metal catalysts and/or external oxidants and thus produce hazardous byproducts and limit the functional group compatibility. Hence, the development of novel and sustainable annulation of biaryl ynones under benign conditions is highly desirable.…”

Iron‐Catalyzed Silylation and Spirocyclization of Biaryl‐Ynones: A Radical Cascade Process toward Silylated Spiro[5.5]trienones

“…Based on the experimental results and previous literatures, [4][5][6][7][8][9][10] a proposed mechanism for the radical cascade reaction is delineated in Scheme 4. Initially, TBHP is decomposed into t-BuO radical and OH radical by heating (path a).…”