Phosphine-Catalyzed Asymmetric Intermolecular Cross-Vinylogous Rauhut–Currier Reactions of Vinyl Ketones with para-Quinone Methides

Primary Aminothiourea-Catalyzed Enantioselective Synthesis of Rauhut-Currier Adducts of 3-Arylcyclohexenone with a Tethered Enone on the Aryl Moiety at the Ortho-Position

An enantioselective synthesis of Rauhut-Currier (RC) adducts from 3-aryl cyclohexenone with a tethered enone moiety at the ortho-position on the aryl group is accomplished. This method provides a wide range of valuable synthetic building blocks having a unique [6-5-6] all-carbon-fused tricyclic skeleton. A primary amine-containing thiourea, a bifunctional organocatalyst, was found to be an efficient catalyst for this transformation. The primary amine counterpart of the catalyst possibly activates the aliphatic enone via dienamine formation (HOMO activation), whereas the thiourea counterpart activates the tethered enone (LUMO activation). Considering the difficulty in achieving an RC reaction of β,β-disubstituted (alkyl and aryl) enones, this method would be significantly rewarding.

Catalyst-Free 1,6-Conjugate Addition/Aromatization/Sulfonylation of para-Quinone Methides: Facile Access to Diarylmethyl Sulfones

An efficient, catalyst-free strategy to construct diarylmethyl sulfones via 1,6-conjugate addition/aromatization/sulfonylation reaction of para-quinone methides with sulfonyl hydrazides under mild and environmentally benign conditions has been developed. The established protocol provided a highly chemo- and regioselectivity synthesis of a diverse array of novel diarylmethyl sulfones with excellent yields, and the reaction could be scaled up.

Asymmetric organocatalytic synthesis of chiral 3,3-disubstituted oxindolesviaa 1,6-conjugate addition reaction

The chiral spirocyclic phosphoric acid-catalyzed enantioselective 1,6-conjugate addition reaction ofpara-quinone methides derived fromN-unprotected isatins with indoles was developed.

Organocatalytic asymmetric synthesis of compounds bearing both isoxazole and pyrazole moieties via 1,6-addition of pyrazol-5-ones to 3-methyl-4-nitro-5-alkenylisoxazoles

Bifunctional thiourea catalyzed 1,6-addition of pyrazol-5-ones to 3-methyl-4-nitro-5-alkenylisoxazoles to provide the desired products in 72–90% yield and 83–94% ee.

A new approach to access difluoroalkylated diarylmethanes via visible-light photocatalytic cross-coupling reactions

A para-quinone methide and difluoroalkylating reagent involved radical cross-coupling reaction was described, through photocatalytically generated diarylmethane radical intermediates.

Catalytic asymmetric 1,6-conjugate addition of in situ generated para-quinone methides with tritylthiol

An asymmetric phase-transfer catalyzed 1,6-conjugate addition of in situ generated para-quinone methides with tritylthiol has been developed.

The [4 + 2] cyclization/retro-Mannich reaction cascade of para-quinone methide derivatives with Pd-containing 1,4-dipoles

The first [4 + 2] cyclization/retro-Mannich reaction cascade of para-quinone methides with Pd-containing 1,4-dipoles generated in situ from vinyl benzoxazinanones has been established. The corresponding rearrangement products were obtained in generally good yields.

Gold-catalyzed tandem reaction of 2-alkynylanilines followed by 1,6-conjugate addition to p-quinone methides: efficient access to unsymmetrical diarylindolylmethanes

A simple, mild, efficient and chemoselective catalytic method for the straightforward synthesis of an interesting class of 2-aryl/alkyl-substituted-3-diaryl indolyl methanes in high yield is reported.

1,6-Conjugated addition-mediated [4 + 1] annulation: an approach to 2,3-dihydrobenzofurans

2,3-Dihydrobenzofurans were achieved via a 1,6-conjugated addition-mediated [4 + 1] annulation of ortho-hydroxyphenyl-substituted para-quinone methides in high yields with high diastereoselectivity.

Asymmetric synthesis of Rauhut–Currier-type esters via Mukaiyama–Michael reaction to acylphosphonates under bifunctional catalysis

A highly enantioselective organocatalytic Mukaiyama–Michael reaction of silyloxy dienes and α,β-unsaturated acyl phosphonates under bifunctional organocatalysis is presented.

Phosphine-Catalyzed Diastereo- and Enantioselective Michael Addition of β-Carbonyl Esters to β-Trifluoromethyl and β-Ester Enones: Enhanced Reactivity by Inorganic Base

A novel chiral biamide-phosphine multifunctional catalyst has been developed that mediates the asymmetric intermolecular Michael addition of β-carbonyl esters to β-trifluoromethyl enones and 3-aroyl acrylates in the presence of competing methyl acrylate and the inorganic base. This method provides a facile access to structurally diverse trifluoromethyl and quaternary stereogenic centers with excellent enantioselectivity (up to 99% ee) and good diastereoselectivity (up to 13:1 dr). The addition of the inorganic base (K₃PO₄) does not cause the background racemic reaction and enhances the reactivity by serving as a co-catalyst.

Ferrocene Derived Bifunctional Phosphine-Catalyzed Asymmetric Oxa-[4+2] Cycloaddition of α-Substituted Allenones with Enones

An efficient ferrocene-derived bifunctional phosphine-catalyzed enantioselective oxa-[4+2] cycloaddition of α-substituted allenones with a broad range of enones is investigated for the preparation of stereodefined dihydropyrans in good to excellent yields (up to 99 %) and excellent enantioselectivity (up to 99 % ee). Furthermore, a series of valuable chiral polyheterocyclic frameworks can be efficiently achieved in good yields with excellent enantioselectivities.

Enantioselective Synthesis of Functionalized 4-Aryl Hydrocoumarins and 4-Aryl Hydroquinolin-2-ones via Intramolecular Vinylogous Rauhut-Currier Reaction of para-Quinone Methides

A novel strategy for the asymmetric construction of functionalized 4-aryl-3,4-dihydrocoumarins and 4-aryl-3,4-dihydroquinolin-2-ones via an intramolecular vinylogous Rauhut-Currier reaction of para-quinone methides (p-QMs) under the bifunctional catalysis of chiral amine-phosphine is described. This intramolecular mode for the catalytic enantioselective 1,6-conjugate addition of p-QMs has been explored for the first time, delivering two types of synthetically important heterocycles in high yields and enantioselectivites.

Phosphine-catalyzed intramolecular Rauhut–Currier reaction: enantioselective synthesis of hydro-2H-indole derivatives

A highly enantioselective intramolecular Rauhut–Currier reaction catalyzed by a multifunctional chiral aminophosphine catalyst was reported.

Phosphine-catalyzed Friedel–Crafts reaction of naphthols with para-quinone methides: expedient access to triarylmethanes

A novel phosphine-catalyzed Friedel–Crafts reaction of naphthols with para-quinone methides has been developed.