Modular Construction of Heterobiaryl Atropisomers and Axially Chiral Styrenes via All-Carbon Tetrasubstituted VQMs.

Here we report a new type of chiral all-carbon tetrasubstituted VQMs generated via chiral phosphoric acids catalyzed nucleophilic addition of 2-alkynylnaphthols to o-quinone methides or imines, which can be captured intramolecularly as a result of cycloaddition reaction. A new class of naphthyl-2H-chromenes bearing axially and centrally chiral elements and axially chiral quinone-naphthols were prepared efficiently with good to excellent yields, diastereoselectivities and enantioselectivities. Noteworthy, the enantioselective cycloaddition of alkynylnaphthols with o-quinone methides proceeded via a [2+2] cycloaddition, followed by a retro-4π-electrocyclization and a 6π re-cyclization. While the cycloaddition of alkynylnaphthols with imines proceeded via a sequential [2+4] cycloaddition and an auto oxidation reaction. Moreover, the obtained axially chiral naphthols can be converted into valuable phosphine ligands and other functional molecules.

A Dehydrogenative Inverse Electron Demand Diels-Alder Reaction for the Synthesis of Functionalized Pyranones.

An efficient dehydrogenative inverse electron demand Diels-Alder reaction of isopropyl and prenyl benzene derivatives with electron-deficient dienes followed by decarboxylation has been reported for the first time. The much broader substrate scope of dienophiles and electron-deficient dienes led to biologically valuable pyranones in good to excellent yields.

Scandium Triflate Catalyzed Tandem Transfer Hydrogenation and Cyclization Reaction of o-Aminobenzaldehydes and o-Aminoacetophenone with Alcohols.

An effective Sc-catalyzed transfer hydrogenation and cyclization tandem reaction has been achieved. This process showed excellent functional group compatibility and good yields. A variety of benzoxazines were produced with primary or secondary alcohols as a hydrogen source. Furthermore, the utility of this newly developed protocol is demonstrated through scaled-up experiment, late-stage modification, and preliminary exploration of enantioselective synthesis.

Selectfluor-Mediated Stereoselective [1 + 1 + 4 + 4] Dimerization of Styrylnaphthols.

Stereoselective [1 + 1 + 4 + 4] dimerization of 1-styrylnaphthols has been developed by using Selectfluor as the oxidant for the first time. The reaction was compatible with various functional groups, giving a class of ethanodinaphtho[b,f][1,5]dioxocines with novel 3D skeletons. DFT calculations indicate that this method merges an intriguing stereoselective intermolecular 1 + 1 radical coupling to construct a bridged C-C bond and then an intramolecular [4 + 4] formal cycloaddition of the in situ generated o-quinone methide intermediate.

Palladium-Catalyzed Site-Selective C(sp3)-H Arylation of Phenylacetaldehydes.

We describe a Pd-catalyzed selective C-H arylation reaction of phenylacetaldehydes using l-valine as the transient directing group. This process showed a broad substrate scope and excellent selectivity in which a ligand-controlled functionalization of the unactivated ß-C(sp3)-H bond. In addition, enantioselective arylation of phenylacetaldehydes was preliminarily explored by utilizing a bulky chiral transient directing group.

Chiral Phosphoric-Acid-Catalyzed Cascade Prins Cyclization.

Asymmetric Prins cyclization of in situ generated quinone methides and o-aminobenzaldehyde has been developed with chiral phosphoric acid as an efficient catalyst. This unconventional method provides a facile access to diverse functionalized trans-fused pyrano-/furo-tetrahydroquinoline derivatives in excellent yield and with excellent diastereo- and enantioselectivities (up to 99% yield and 99% ee). Mechanistic studies suggested that the three adjacent tertiary stereocenters were constructed through the sequential formation of C-O, C-C, and C-N bonds.

Phenanthrene Synthesis by Palladium(II)-Catalyzed γ-C(sp2)-H Arylation, Cyclization, and Migration Tandem Reaction.

Phenanthrene is an important structural motif in chemistry and materials science, and many synthetic routes have been developed to construct its skeleton. However, synthesis of unsymmetric phenanthrenes remains a challenge. Here, an efficient one-pot tandem reaction for the preparation of phenanthrenes via sequential γ-C(sp2)-H arylation, cationic cyclization, dehydration, and 1,2-migration was developed. A wide range of symmetric and unsymmetric phenanthrenes with diversified functional groups were synthesized with good to excellent yields.

Enantioselective [3 + 2] Formal Cycloaddition of 1-Styrylnaphthols with Quinones Catalyzed by a Chiral Phosphoric Acid.

The first highly enantioselective [3 + 2] formal cycloaddition of 1-styrylnaphthols (or phenol) with quinones catalyzed by a chiral phosphoric acid has been reported. A class of trans-2,3-diarylbenzofurans were prepared efficiently (up to 99% yield, >20:1 dr, 99% ee). This organocatalytic procedure allows lowering of the catalyst loading to 0.5 mol % without considerable loss in reactivity and enantioselectivity.

Enantioselective Organocatalytic Sulfenylation of ß-Naphthols.

An enantioselective sulfenylation of ß-naphthols has been developed for the first time using a newly synthesized cinchona-derived thiourea as the catalyst and N-(arylthio) succinimide (or phthalimide) as an electrophilic sulfur source. Various enantioenriched naphthalenones with an S-containing all-substituted stereocenter were prepared via a dearomatization strategy under mild reaction conditions.

Asymmetric Arylative Dearomatization of ß-Naphthols Catalyzed by a Chiral Phosphoric Acid.

An enantioselective arylative dearomatization reaction of ß-naphthols with quinone monoimides has been developed for the first time using a chiral phosphoric acid as the catalyst, the desired enantioenriched cyclohexadienones were prepared with excellent yields and enantioselectivities by a domino Michael addition and aromatization process (up to 99 % yield, up to 98 % ee). This process is operationally simple and readily scaled up, as well as a broad substrate scope which includes 1-substituted-2-naphthols with/without 3-substituents. Furthermore, this organocatalytic procedure allows the lowering of catalyst loading to 0.5 mol % without considerable loss in reactivity and enantioselectivity.