A catalytic carbonylative double cyclization method for the synthesis of furo­[3,4-b]­benzofuran-1­(3H)-ones is reported. It is based on the reaction between readily available 2-(3-hydroxy-1-yn-1-yl)­phenols, CO, and oxygen carried out in the presence of catalytic amounts of PdI2 (1 mol %) in conjunction with KI (20 mol %) and 2 equiv of diisopropylethylamine at 80 °C for 24 h under 30 atm of a 1:4 mixture of CO–air. Interestingly, the process was not selective when carried out in classical organic non-nucleophilic solvents (such as MeCN or DME), leading to a mixture of the benzofurofuranone derivative and the benzofuran ensuing from simple cycloisomerization, whereas it turned out chemoselective toward the formation of the double cyclization compound in BmimBF4 as the reaction medium. Moreover, the ionic liquid solvent containing the catalyst could be easily recycled several times without appreciable loss of activity.

The control of the stereochemistry of macromolecules is a very important goal, and coordination-insertion polymerization is superior with respect to the other polymerization methods for its achievement. In this contribution, we focus on Pd(II) homogeneous catalysts for the stereocontrolled synthesis of CO/vinyl arene polyketones. We developed a library of aldo-and keto-iminopyridine ligands N-N′ that feature an αor β-naphthyl or anthracenyl moiety on the imino nitrogen atom (N imm ). With such ligands, the Pd(II) monocationic complexes [Pd(CH 3 )(CH 3 CN)-(N-N′)][PF 6 ] were synthesized. NMR spectroscopy shows that in solution, each complex exists as an equilibrium mixture of cis and trans stereoisomers, the latter having the CH 3 ligand opposite to the Pd−N imm bond. The isomeric population depends on the N-N′ ligand: an almost 1:1 ratio is found for the ketimine complexes, whereas those with the aldimines show a preference for the trans geometry. These complexes generate very efficient catalysts for the CO/vinyl arene copolymerization. Catalyst performances depend both on the nature of N-N′ and of the vinyl arene comonomer. The ketimine-based catalysts are more stable and more productive than the aldimine counterpart, leading to prevailingly syndiotactic macromolecules of high M w (up to 280 kDa). The aldimine derivatives produce copolymers with isotactic and syndiotactic stereoblocks of different lengths depending on the vinyl arene. The effect of the prochiral monomer on the copolymer tacticity is steric in nature as demonstrated by the stereochemistry of the obtained CO/4-fluorostyrene polyketone, whose synthesis is reported here for the first time. As a conclusion, we have now demonstrated that when catalysts with nonsymmetric ancillary ligands are used, and stereoisomers are present, the stereochemistry of the copolymerization is driven by both the catalyst isomeric distribution and the prochiral comonomer.

This report demonstrates the possibility of a nickel-catalyzed difunctionalization of unactivated alkenes initiated by an unstabilized enolate nucleophile. The process tolerates a diverse range of electrophiles, including aryl, heteroaryl, alkenyl, and amino electrophiles. An electron-deficient phosphine ligand and a tetrabutylammonium salt additive were crucial for promoting efficient vicinal difunctionalization.

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The first example of the bis-alkoxycarbonylation of acrylic esters and acrylic amides, leading to differently substituted 1,1,2-ethanetricarboxylate compounds and 2-carbamoylsuccinates respectively, is reported. The catalyst is formed in situ by mixing Pd(TFA) 2 (TFA = trifluoroacetate) and the ligand bis(2,6dimethylphenyl)butane-2,3-diimine. The reaction, that proceeds using p-benzoquinone as oxidant and ptoluenesulfonic acid as additive, has been applied to variously substituted electron-poor alkenes, employing different alcohols as nucleophiles, under very mild reaction conditions (4 bar of carbon monoxide at 20°C). Remarkably, this catalytic system is able to promote the carbonylation of both the β-and the generally unreactive α-positions of acrylic esters and amides, allowing the formation of bis-alkoxycarbonylated products in good to excellent yields (up to 98%). The trend of reactivity, observed with the different electron-deficient olefins, has been rationalized on the basis of the proposed catalytic cycle and DFT calculations.