Metal‐free Synthesis of Spiro‐2,2′‐benzo[b]furan‐3,3′‐ones via PhI(OAc)₂‐Mediated Cascade Spirocyclization

Abstract

Treating the benzyl protected 3‐hydroxy‐1,3‐bis(2‐hydroxyphenyl)prop‐2‐en‐1‐ones solely with PhI(OAc)2 (PIDA) in DCE at room temperature readily furnished the seldom studied spiro‐2,2′‐benzo[b]furan‐3,3′‐ones in satisfactory to excellent yields. The hypervalent iodine reagent enables the metal‐free cascade spirocyclization resulting in the dual oxidative C−O bond formation.magnified image

Synthesis of Spiro[benzofuran‐2,2'‐benzo[b]thiophene]‐3,3'‐diones via PIDA/CuBr‐Mediated Spirocyclization

“…[ 10 ] In our previous work, we have realized the construction of spiro‐2,2'‐benzo[ b ]furan‐3,3'‐one skeleton through a PIDA‐mediated spirolization of benzyl protected 3‐hydroxy‐1,3‐bis(2‐hydroxyphenyl)prop‐2‐en‐1‐ones, during the process of which dual intramolecular C–O bond forming reaction occurs. [ 11 ] In continuation of our interest in the assemblage of spiroheterocyclic framework, [ 6e–6g,12 ] we were motivated to investigate whether we could combine the strategy of transition‐metal mediated aryl C(sp 2 )–S bond formation with that of the PIDA‐mediated C–O/C–S bond formation to produce the S‐containing 3 H ,3' H ‐spiro[benzofuran‐2,2'‐benzo[ b ]thiophene]‐3,3'‐dione compound, an analogue of the previously reported spiro‐2,2'‐benzo[ b ]furan‐3,3'‐one compound.…”

Enroute sustainability: metal free C–H bond functionalisation

“…Recently in 2019, the same group reported a PIDA-mediated intramolecular dual oxidative C–O bond formation of protected 3-hydroxy-1,3-bis(2-hydroxyaryl)pro p -2- en -1-ones 146a for the efficient synthesis of spiro-benzo[ b ]furan-3-one derivatives 146b in good to excellent yield (Scheme 146). 187 A wide variety of substrates bearing either electron-donating groups or electron-withdrawing groups were well tolerated under this reaction condition.…”

Synthesis, XRD and Mechanistic Studies of α‐Aryl‐β,β‐ditosyloxy Ketones: An Oxidative 1,2‐Aryl Migration in α,β‐Unsaturated Diaryl Ketones Under Metal Free Conditions

“…These reagents are non‐toxic, mild, efficient, environmentally benignant and having multipurpose oxidative characteristics over heavy metal reagents such as thallium (Tl) and lead (Pb) in their different transformation [1] . The examples of hypervalent iodine(III) reagents mediated transformations includes asymmetric α‐functionalization of carbonyl compounds, [2] trifluoromethylthiolation, [3] oxidative rearrangement, [4] ring‐contraction, [5] ring‐expansion, [6] spirocyclization, [7] alkene dimerization [8] and oxytosylation followed by heterocyclization [9] etc. The synthetic renaissance of hypervalent iodine(III) compounds as effective functional‐group transfer reagent also unprecedently explored specifically in arenas of oxidative difunctionalization [10] of olefinic skeleton, exemplified as enantioselective diamination, [11] thioamination, [12] enantioselective diacetoxylation, [13] oxyamination, [14] aminofluorination [15] and 1,2‐difluorination [16] .…”