Selenium‐Catalyzed C(sp³)H Acyloxylation: Application in the Expedient Synthesis of Isobenzofuranones

Abstract

Oxidative Se-catalyzed C(sp3)-H bond acyloxylation has been used to construct a diverse array of isobenzofuranones from simple ortho-allyl benzoic acid derivatives. The synthetic procedure employs mild reaction conditions and gives high chemoselectivity enabled by an inexpensive organodiselane catalyst. The presented approach offers a new synthetic pathway toward the core structures of phthalide natural products.

Catalyst‐Enabled Site‐Divergent Stereoselective Michael Reactions: Overriding Intrinsic Reactivity of Enynyl Carbonyl Acceptors

“…The actual synthesis was initiated by quantitative conversion of 1,6‐γ‐ Z , E ‐ 5 a into the hydroxy carboxylic acid 8 in a three‐step sequence, that is, azlactone ring‐opening with methanol under mildly acidic conditions, reduction of the N ‐acyl pyrazole group with NaBH 4 , and subsequent saponification of the methyl ester. By taking advantage of the remaining diene moiety in 8 , the δ‐valerolactone 9 was produced by a diastereoselective selenolactonization followed by the removal of the vicinal hydroxy and selenenyl groups . Then, selective ozonolysis of the pendant vinyl group was reductively quenched with NaBH 4 and, after reduction of the lactone carbonyl, diastereoselective syn ‐dihydroxylation of the endocyclic olefin, by a modification of Baran's procedure, yielded the azasugar derivative 10 .…”

A novel approach to oxoisoaporphine alkaloids via regioselective metalation of alkoxy isoquinolines

“…For the introduction of ring D of the oxoisoaporphine alkaloids one common building block, (4-methoxy-2-(methoxycarbonyl)phenyl)boronic acid pinacol ester ( 9 ) [ 24 ], could be applied, since the alkaloids of interest all bear the methoxy group at C-9. Suzuki cross-coupling reaction of the iodinated isoquinolines 8a – c with this boronate under Pd(PPh 3 ) 4 catalysis gave the desired 1-arylisoquinolines 10a–c in moderate to good isolated yields (65–77%, Scheme 3 ).…”

Vinylidene Homologation of Boronic Esters and its Application to the Synthesis of the Proposed Structure of Machillene

“…for am echanistic proposal). [35] Thee nd game was particularly challenging and required (i)selective reaction of the styrene over the 1,1-disubstituted alkene (ii)reagent-controlled diastereoselective epoxidation (iii)isolation of the monoepoxide from the statistical mixture of SM, mono-and di-epoxides that would be expected. Following this reaction, as econd epoxidation of the monoepoxide with the enantiomeric epoxidation reagent should occur on the remaining styrene with the correct stereochemical outcome.Our initial attempts were based around the Shi epoxidation but no conversion to the desired mono-epoxide 19 was observed and instead starting material was recovered.…”