Pd(II)-Catalyzed Cascade Wacker−Heck Reaction:  Chemoselective Coupling of Two Electron-Deficient Reactants

Abstract

A novel palladium(II)-catalyzed oxy-carbopalladation process was developed allowing for the orchestrated union of hydroxy ynones with ethyl acrylate, two electron-deficient reactants. With beta-hydroxy ynones, this cascade Wacker-Heck process gave access to highly functionalized tri- or tetrasubstituted dihydropyranones featuring an unusual dienic system. For diastereomerically pure and for enantioenriched beta-hydroxyynones, these reactions proceed without affecting the stereochemical integrity of the existing stereocenters. In addition, tetrasubstituted furanones can be prepared when alpha-hydroxyynones and ethyl acrylate are used as starting materials. The dihydropyranones and furanones obtained upon cyclization are novel compounds, but structurally related carbohydrate derivatives featuring a similar dienic system have been used as starting materials for the construction of polyannulated products, suggesting that these cascade Pd(II)-mediated oxidative heterocyclizations are of value for various synthetic applications.

A facile base-promoted domino Michael/O-alkylation reaction for the construction of succinimide-substituted 3(2H)-furanones

“…Under the optimal reaction conditions, the generality of this protocol was studied (Table 3). Firstly, a wide range of maleimides 1a-n was studied (Table 3, entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The maleimides included those bearing electronwithdrawing and electron-donating substituents on the aryl ring, as well as N-alkyl maleimides.…”

“…[1][2][3][4] The significance of these molecules has led to a variety of approaches for the synthesis of substituted 3(2H)-furanones, including acid-catalyzed cyclization-dehydration, 5,6 transformations from furans, 7,8 alkynes [9][10][11][12][13][14][15] and allenes. 16 However, most of these routes require the use of specific substrates and reaction conditions are often harsh.…”

Metalated Chromene and Chromone Complexes: pH Switchable Metal–Carbon Bonding Interaction, Photo‐triggerable Chromone Delivery Application, and Antioxidative Activity

“…The molecular structures for [ 1 (Cl)] 2 ⋅CH 3 OH, 3 (Cl)⋅2 CH 2 Cl 2 and 4 ⋅CH 3 OH determined by X‐ray crystallography (Figure ) represent the first examples of metalated chromene and chromone complexes through transition‐metal‐mediated cyclization of phenol‐tethered ynone ,. In each case, the Ru atom adopts a distorted octahedral geometry, with the chromene or chromone ligand metalated at its C‐2 position and coordinated in a monodentate fashion.…”

Asymmetric Domino Reactions Based on the Use of Chiral Substrates

“…81 After b-hydride elimination, the trisubstituted dihydropyranone was formed with concomitant formation of a palladium hydride species which could, upon reductive elimination, allow Pd(0) to re-enter the catalytic cycle after oxidation by molecular oxygen. The first total synthesis of natural biologically active (-)-panacene was accomplished by Snieckus et al on the basis of a key asymmetric domino alkoxycarbonylation-lactonisation reaction of a chiral phenol with retention of enantioselectivity, as shown in Scheme 1.51.…”