Diastereoselective synthesis of chroman bearing spirobenzofuranone scaffolds via oxa-Michael/1,6-conjugated addition of para-quinone methides with benzofuranone-type olefins

A simple and convenient cyclization of ortho-hydroxyphenyl-substituted para-quinone methides with benzofuran-2-one type active olefins via oxa-Michael/1,6-conjugated addition has been developed, which afforded an easy access to enriched functionalized chroman-spirobenzofuran-2-one scaffolds with good to excellent yields (up to 90%) and diastereoselectivities (up to >19 : 1 dr). This reaction provided an efficient method for constructing desired spirocyclic compounds combining both well-known heterocyclic pharmacophores chroman and benzofuran-2-one.

Highly diastereoselective synthesis of spirocyclic compounds combining both well-known heterocyclic pharmacophores chroman and benzofuran-2-one.

Direct Synthesis of 3-Coumaranones with Calcium Carbide as an Acetylene Source

A novel synthesis method for the construction of 3-coumaranones from the reaction of two molecules, calcium carbide and salicylaldehyde, was reported. Various 2-methyl-2-vinylbenzofuran-3(2H)-ones could be obtained in moderate yields in the absence of a metal catalyst. The salient features of this protocol involve widely available starting materials, an inexpensive and easy-to-handle alkyne source, and a cost-efficient route. The reaction mechanism was verified by density functional theory calculations of possible intermediates and corresponding transition states.

Phosphine Organocatalysis

The hallmark of nucleophilic phosphine catalysis is the initial nucleophilic addition of a phosphine to an electrophilic starting material, producing a reactive zwitterionic intermediate, generally under mild conditions. In this Review, we classify nucleophilic phosphine catalysis reactions in terms of their electrophilic components. In the majority of cases, these electrophiles possess carbon-carbon multiple bonds: alkenes (section 2), allenes (section 3), alkynes (section 4), and Morita-Baylis-Hillman (MBH) alcohol derivatives (MBHADs; section 5). Within each of these sections, the reactions are compiled based on the nature of the second starting material-nucleophiles, dinucleophiles, electrophiles, and electrophile-nucleophiles. Nucleophilic phosphine catalysis reactions that occur via the initial addition to starting materials that do not possess carbon-carbon multiple bonds are collated in section 6. Although not catalytic in the phosphine, the formation of ylides through the nucleophilic addition of phosphines to carbon-carbon multiple bond-containing compounds is intimately related to the catalysis and is discussed in section 7. Finally, section 8 compiles miscellaneous topics, including annulations of the Hüisgen zwitterion, phosphine-mediated reductions, iminophosphorane organocatalysis, and catalytic variants of classical phosphine oxide-generating reactions.

Chiral phosphine-catalyzed tunable cycloaddition reactions of allenoates with benzofuranone-derived olefins for a highly regio-, diastereo- and enantioselective synthesis of spiro-benzofuranones

The first regioselective catalytic asymmetric [3 + 2] cycloaddition of benzofuranone-derived olefins with allenoates and substituted allenoates has been developed in the presence of (R)-SITCP, affording different functionalized 3-spirocyclopentene benzofuran-2-ones in good yields with high enantioselectivities under mild conditions. The substrate scope has also been examined. The regioselective outcomes for this phosphine-catalyzed [3 + 2] cycloaddition reaction can be rationalized using DFT calculations.

Highly enantioselective Michael addition reactions of 2-substituted benzofuran-3(2H)-ones to nitroolefins

A highly enantioselective Michael addition reaction of 2-substituted benzofuran-3(2H)-ones to nitroolefins was promoted by a bifunctional squaramide catalyst. As a result, a number of chiral 2,2'-substituted benzofuran-3-one derivatives, bearing adjacent quaternary-tertiary stereocenters, were efficiently synthesized with excellent enantioselectivities.

Phosphine-mediated reaction of 3-methyl allenoate and isatins: a protocol for the synthesis of spirofuran oxindoles

A facile synthesis of spirofuran oxindoles via phosphine-mediated reaction of 3-alkyl allenoate with isatins is presented.

Enantioselective Black rearrangement catalyzed by chiral bicyclic imidazole

A newly developed chiral imidazole nucleophilic catalyst, , was readily prepared and successfully applied to the enantioselective Black rearrangement with up to 88% ee for a wide range of substrates possessing different substituted groups. A plausible mechanism for the high enantioselectivity was proposed.