Recent advances in the chemistry of triaryl- and triheteroarylmethanes

LDA-mediated synthesis of ortho-cyanated diarylmethanes by reaction of fluoroarene with arylacetonitrile at room temperature

An efficient and facile method for the synthesis of ortho-cyanated diarylmethane by reaction of fluoroarene with arylacetonitrile in the presence of LDA (lithium diisopropylamide) at room temperature was developed.

Expedient Access to Unsymmetrical Diarylindolylmethanes through Palladium-Catalyzed Domino Electrophilic Cyclization-Extended Conjugate Addition Approach

A palladium-catalyzed domino process to access unsymmetrical diarylindolylmethanes has been developed through the annulation of o-alkynylanilines followed by 1,6-conjugate addition with p-quinone methides (p-QMs) under relatively mild conditions. The broad substrate scope of this methodology was demonstrated through the use of a wide range of substituted o-alkynylanilines and p-quinone methides, and in most cases, the unsymmetrical diarylindolylmethanes could be prepared in moderate to excellent yields. Notably, this method does not require any amino group protection. Moreover, 100% atom economy makes this transformation attractive from a green chemistry perspective.

Selective synthesis of either enantiomer of an anti-breast cancer agent via a common enantioenriched intermediate

A stereoselective synthesis of a bioactive triarylmethane is described. Key to the synthesis is a nickel-catalyzed Suzuki-Miyaura coupling which proceeds with retention at the benzylic center. This method is complementary to our previously reported nickel-catalyzed Kumada coupling which proceeds with inversion. Together, the two methods allow for efficient access to either enantiomer of biologically relevant triarylmethanes from a common enantioenriched intermediate.

In situ activation of benzyl alcohols with XtalFluor-E: formation of 1,1-diarylmethanes and 1,1,1-triarylmethanes through Friedel–Crafts benzylation

The Friedel–Crafts benzylation of arenes using benzyl alcohols activated in situ with XtalFluor-E is described. A wide range of 1,1-diarylmethanes and 1,1,1-triarylmethanes were prepared under simple and mild conditions, without the need for a transition metal or a strong Lewis acid.

Deep eutectic solvent catalyzed Friedel–Crafts alkylation of electron-rich arenes with aldehydes

In this study, six deep eutectic solvents were synthesized. Research shows that [ChCl][ZnCl₂]₂ can be used for catalyzing F–C alkylations of electron-rich arenes with aldehydes successfully. After five cycles, the yields remain about 89–94%.

Diversity oriented synthesis of tri-substituted methane containing aminouracil and hydroxynaphthoquinone/hydroxycoumarin moiety using organocatalysed multicomponent reactions in aqueous medium

One-pot multicomponent reaction of aldehyde, 1,3-dimethyl-6-aminouracil and 2-hydroxy-1,4-naphthoquinone/4-hydroxycoumarin using a bifunctional thiourea-based organocatalyst in aqueous medium has been reported.

Ni(ii) source as a pre-catalyst for the cross-coupling of benzylic pivalates with arylboronic acids: facile access to tri- and diarylmethanes

Various di- and triarylmethanes were synthesized via Ni^II–(σ-aryl) complex-catalyzed Suzuki–Miyaura cross-coupling of benzylic pivalates with arylboronic acids under mild conditions.

NiXantphos: a deprotonatable ligand for room-temperature palladium-catalyzed cross-couplings of aryl chlorides

Although the past 15 years have witnessed the development of sterically bulky and electron-rich alkylphosphine ligands for palladium-catalyzed cross-couplings with aryl chlorides, examples of palladium catalysts based on either triarylphosphine or bidentate phosphine ligands for efficient room temperature cross-coupling reactions with unactivated aryl chlorides are rare. Herein we report a palladium catalyst based on NiXantphos, a deprotonatable chelating aryldiphosphine ligand, to oxidatively add unactivated aryl chlorides at room temperature. Surprisingly, comparison of an extensive array of ligands revealed that under the basic reaction conditions the resultant heterobimetallic Pd–NiXantphos catalyst system outperformed all the other mono- and bidentate ligands in a deprotonative cross-coupling process (DCCP) with aryl chlorides. The DCCP with aryl chlorides affords a variety of triarylmethane products, a class of compounds with various applications and interesting biological activity. Additionally, the DCCP exhibits remarkable chemoselectivity in the presence of aryl chloride substrates bearing heteroaryl groups and sensitive functional groups that are known to undergo 1,2-addition, aldol reaction, and O-, N-, enolate-α-, and C(sp²)–H arylations. The advantages and importance of the Pd–NiXantphos catalyst system outlined herein make it a valuable contribution for applications in Pd-catalyzed arylation reactions with aryl chlorides.

Synthesis of enantiomerically enriched triarylmethanes by enantiospecific Suzuki-Miyaura cross-coupling reactions

The Suzuki-Miyaura cross-coupling of chiral, enantiomerically enriched dibenzylic boronic esters is described. The reaction proceeds with almost complete retention of stereochemistry, providing access to triarylmethanes, compounds that have high biological activity and are difficult to prepare in enantiomerically pure form using other methods.

Enantioselective synthesis of triarylmethanes by chiral imidodiphosphoric acids catalyzed Friedel-Crafts reactions

The first enantioselective synthesis of pyrrolyl-substituted triarylmethanes has been accomplished using a novel imidodiphosphoric acid catalyst, which is derived from two (R)-BINOL frameworks with different 3,3'-substituents. This strategy was also expanded to the synthesis of bis(indolyl)-substituted triarylmethanes with high enantioselectivities, which could only be obtained with moderate ee values in previous reports. These two efficient Friedel-Crafts alkylation processes feature low catalyst loading, broad functional group compatibilities, and the potential to provide practical pathways for the synthesis of enantioenriched bioactive triarylmethanes.

Synthetic methodologies of achiral diarylmethanols, diaryl and triarylmethanes (TRAMs) and medicinal properties of diaryl and triarylmethanes-an overview

This review covers the synthesis of achiral diarylmethanols, diaryl and triarylmethanes and the bioactivities of diaryl and triarylmethanes during 1995 to 2013.

Synthesis and X-ray crystal structure of isomeric pyridine-based leuco-TAM dyes, 2,2-(2-(pyridinyl)propane-1,3-diylidene)bis(5-chloro-1,3,3-trimethyl indoline) derivatives and unusual stability of 4-pyridinyl compound

The solid-state structures and unequivocal stereochemistries of isomeric pyridine-based leuco-triarylmethane (LTAM) dyes 2,2'-(2-(pyridin-4 or 3-yl)propane-1,3-diylidene)bis(5-chloro-1,3,3-trimethylindoline) derivatives were established by X-ray crystallography. Surprisingly, the EE isomer was formed for the 4-pyridinyl compound, whereas the 3-pyridinyl compound formed ZE isomers. In addition, the latter have a so-called three-bladed propeller conformation, whereas the former possess a Y-shaped conformation. These pyridine-based LTAM compounds stack to form a dimer, adopting either an orthorhombic, with Pcmn space group, or monoclinic crystal system with P21/n space group in the crystal unit cell.

Taming furfuryl cations for the synthesis of privileged structures and novel scaffolds

Furfuryl cations are generated via a highly efficient bismuth-catalyzed reaction of furfuryl alcohols. This systematic study provides insight on the reactivity profile of furfuryl cations towards nucleophilic substitution reactions. Novel C-C, C-N, C-O and C-S bond forming reactions of furfuryl cations have been developed, thus providing access to a diverse array of building blocks for further manipulations.