Palladium-Catalyzed Addition of Arylboronic Acids topara- Quinone Methides for Preparation of Diarylacetates

Magnesium-Mediated Umpolung Carboxylation of p-Quinone Methides with CO2

Magnesium-mediated reductive carboxylation of p-QMs with CO2 via an Umpolung strategy has been developed, which can be used for the preparation of various aryl acetic acids. This protocol featured high atom economy, mild conditions, and operational simplicity. The creation of this Umpolung carboxylation of p-QMs will unprecedentedly extend the application of p-QMs to nucleophilic reagents.

Asymmetric cross Rauhut–Currier reactions of vinyl ketones with carbonyl para-quinone methides via phosphine catalysis

Novel cross Rauhut–Currier reactions, involving chiral phosphine catalysis, between vinyl ketones and terminal-carbonyl-substituted para-quinone methides are presented.

Iron catalyzed tandem ring opening/1,6-conjugate addition of cyclopropanols with p-quinone methides: new access to γ,γ-diaryl ketones

An iron(III) catalyzed tandem ring opening/1,6-conjugate addition of cyclopropanols to p-quinone methides leading to γ,γ-diaryl ketones has been described. This catalytic protocol provides a novel and efficient method to access γ,γ-diaryl ketone derivatives in good to excellent yields with high functional group tolerance. Importantly, γ,γ-diaryl ketone can be further functionalized to give a versatile set of useful products.

Phosphine-Catalyzed Intermolecular Dienylation of Alkynoate with para-Quinone Methides

An interesting remote δ-C 1,6-addition and an isomerization cascade reaction for phosphine-catalyzed activated alkynes have been disclosed. The products featuring a functional diene and a 1,1-diaryl methyl motif have been obtained in moderate to good yields (30-86%) by applying para-quinone methides (p-QMs) and δ-substituted alkynoate with tributylphosphine (PⁿBu₃) catalysis, along with high regioselectivity and stereoselectivity (dr > 20:1). The wide scope of compatible substrates (35 examples), such as indolyl, oxindolyl, ester, and cinnamyl, expand the utility of this methodology. A plausible mechanism and some applications of it have also been presented.

Construction of fully substituted carbon centers containing a heteroatom and a CF3 group via in situ generated p-quinone methides

1,6-Conjugate additions of in situ generated δ-CF3-δ-substituted p-quinone methides have been achieved with a variety of heteronucleophiles under mild conditions, which led to facile and practical construction of fully substituted carbon centers including a heteroatom and a CF3 group. In particular, it was revealed that some amines themselves worked for efficient cleavage of the TBS protective group, and addition of a catalytic amount of an appropriate Brønsted acid was found to sometimes improve the progress of the desired process.

Uranyl-catalyzed hydrosilylation of para-quinone methides: access to diarylmethane derivatives

An efficient and convenient uranyl-catalyzed reductive hydrosilylation reaction of para-quinone methides (p-QMs) was developed by employing silane as the reductant. The hydrosilylation procedure using the UO2(NO3)2·6H2O/Et3SiH catalytic system proceeded smoothly and provided an expedient method for the construction of various diarylmethane derivatives in one step with good to excellent yields.

Catalytic Friedel-Crafts Alkylation of Electron Rich Aromatic Derivatives with α-Aryl Diazoacetates Mediated by Brønsted Acids

The catalytic protonation of aryl diazoacetates by strong Brønsted acids, followed by a Friedel-Crafts alkylation reaction with electron rich aromatic compounds, is reported. The reaction provided in a direct fashion 24 geminal diarylacetates in yields of ≤92%.

Recent developments in 1,6-addition reactions of para-quinone methides (p-QMs)

In this review, we provide a comprehensive overview of recent progress in this rapidly growing field by summarizing the 1,6-conjugate addition and annulation reactions of p-QMs with consideration of their mechanisms and applications.

InCl3-catalyzed 5-exo-dig cyclization/1,6-conjugate addition of N-propargylamides with p-QMs to construct oxazole derivatives

An InCl₃-catalyzed tandem intramolecular 5-exo-dig cyclization/1,6-conjugate addition/aromatization of N-propargylamides with p-QMs to produce oxazoles tethering diarylmethane has been successfully developed.

Mn-Catalyzed 1,6-conjugate addition/aromatization of para-quinone methides

A series of ferrocenyl triazole ligands have been synthesized and characterized, which proved to be effective for the Mn-catalyzed 1,6-conjugate addition/aromatization of para-quinone methides with good to high yields under mild conditions. This protocol provided an efficient and practical route to the synthetically interesting functionalized quinones, methines and their analogues.

Pd(ii)-Catalyzed asymmetric 1,6-conjugate addition of arylboronic acids to Meldrum's acid-derived dienes

A Pd(ii)-catalyzed asymmetric 1,6-conjugate addition of arylboronic acids to Meldrum's acid-derived dienes has been realized using a new pyridine–oxazoline ligand bearing an extended arm.

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.

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.

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.

B(C6F5)3 catalysed reduction of para-quinone methides and fuchsones to access unsymmetrical diaryl- and triarylmethanes: elaboration to beclobrate

An effective method for the synthesis of diaryl- and triarylmethane derivatives through a Lewis acid catalyzed reduction of para-quinone methides and fuchsones, respectively, using the Hantzsch ester as a hydride surrogate is described.