H3PMo12O40-catalyzed coupling of diarylmethanols with epoxides/ diols/aldehydes toward polyaryl-substituted aldehydes

A versatile heteropoly acid (H₃PMo₁₂O₄₀)-catalyzed coupling of diarylmethanols with epoxides was established for the synthesis of polyaryl-substituted aldehydes. Furthermore, the catalytic system was also suitable for the reaction of diarylmethanols and diols/aldehydes. The application of such an earthabundant, readily accessible, and nontoxic catalyst provides a green approach for the construction of polyaryl-substituted aldehydes.     

Nickel salt-catalyzed addition reaction of arylboronic acids to aromatic aldehydes

Arylation reaction of aromatic aldehydes with arylboronic acids proceeded smoothly in the presence of a base and catalytic amount of a nickel salt, Ni(ClO₄)₂·6H₂O, in toluene/IPA = 5:1 or IPA to afford corresponding diarylmethanols in good to excellent yields.     

Microwave-assisted nickel(II) acetylacetonate-catalyzed arylation of aldehydes with arylboronic acids

Applying sealed vessel microwave heating at 180 °C in toluene the arylation of aromatic and aliphatic aldehydes with arylboronic acids using 1-2 mol % of Ni(acac)₂ as a catalyst can be performed efficiently within 10-30 min providing the desired diarylmethanols or benzyl alcohols in good yields.     

Enantioselective arylation of aldehydes catalyzed by a soluble optically active polybinaphthols ligand

A soluble chiral polymer ligand was synthesized by the polymerization of (R)-6,6′-dibutyl-3,3′-diformyl-2,2′-binaphthol (R-M-1) with 2,5-diaminopyridine (M-2) via a nucleophilic addition-elimination reaction. While arylboronic acids were used as the source of the transferable aryl group, the chiral polybinaphthols ligand in combination with Et₂Zn without Ti(OⁱPr)₄ exhibited higher enantioselectivity in asymmetric addition to aromatic aldehydes than alphatic aldehydes. When aromatic aldehydes with electron-withdrawing groups were chosen as substrates, the resulting diarylmethanols were produced in higher ee values than those with electron-donating groups as substrates. 2-Naphthaldehyde used as a substrate afforded product in 95% ee, which could be ascribed to the steric effect influence on this asymmetric arylation reaction. Moreover, the chiral polymer was easily recovered and reused, but exhibited a decrease of enantioselectivity in the third recycle.     

Synthesis of new alkoxy/sulfonate-substituted carbene precursors derived from [2.2]paracyclophane and their application in the asymmetric arylation of aldehydes

A series of novel planar chiral alkoxy/sulfonate-substituted carbene precursors have been designed and synthesized. They were used as N-heterocyclic carbene ligands in the Rh-catalyzed asymmetric addition of arylboronic acids to aromatic aldehydes, affording chiral diarylmethanols with high yields and moderate enantioselectivities.     

Highly enantioselective addition of in situ prepared arylzinc to aldehydes catalyzed by a series of atropisomeric binaphthyl-derived amino alcohols

The direct addition of in situ prepared arylzinc to aldehydes with chiral binaphthyl-derived amino alcohols as catalysts can afford optically active diarylmethanols in high yields and with excellent enantioselectivities (up to 99 % ee, ee = enantiomeric excess). By using a single catalyst, both enantiomers of many pharmaceutically interesting diarylmethanols can be obtained by the proper combination of various arylzinc reagents with different aldehydes; this catalytic system also works well for the phenylation of aliphatic aldehydes to give up to 96 % ee.     

Carbinol derivatives via rhodium-catalyzed addition of potassium trifluoro(organo)borates to aldehydes

Reaction of potassium aryltrifluoroborates with aldehydes, in the presence of a rhodium catalyst, afforded carbinol derivatives in high yields under mild aqueous conditions; this efficient reaction proved to be general, allowing the production of highly hindered diarylmethanols and aliphatic aldehydes were also reactive under these conditions.     

New class of amino-phosphinite chiral catalysts for the highly enantioselective addition of arylzinc reagents to aldehydes

A new class of amino-phosphinite chiral ligands was prepared and applied in zinc-catalyzed addition of aryl boronic acids to aldehydes; the reaction furnished the diarylmethanols in excellent yields and with a high level of enantioselectivity (up to 93% ee).     

Polystyrene-supported amino alcohol ligands for the heterogeneous asymmetric addition of phenyl zinc reagents to aldehydes

A family of polystyrene-supported amino alcohols, characterized by a high catalytic activity in alkyl transfer from zinc to formyl groups has been successfully tested in the enantioselective addition of phenyl zinc reagents to aldehydes to afford chiral diarylmethanols. Enantioselectivities higher than 90% (mean ee 90.5%; eight examples) are recorded with aromatic aldehydes in what represents the first successful use of heterogeneous, polymeric reagents for enantiocontrol in the phenylation of aldehydes.     

Synthesis of gem-difluorides from aldehydes using DFMBA

Synthesis of gem-difluorides from aldehydes was effectively achieved using DFMBA and Et₃N-3HF under microwave irradiation or conventional thermal heating. Both aromatic and aliphatic aldehydes could be converted to the corresponding gem-difluorides in good yields.     

Remarkably efficient enantioselective titanium(IV)-(R)-H8-BINOLate catalyst for arylations to aldehydes by triaryl(tetrahydrofuran)aluminum reagents

Novel asymmetric triarylaluminum AlAr3(THF) additions to aldehydes catalyzed by 10 mol % of the titanium(IV) complex of (R)-H8-BINOL ligand are reported. The catalytic system is extremely efficient with reactions completing within 10 min. The system applies to the most diversified aldehydes to date, and more than 20 aldehydes were examined to afford diarylmethanols having an electron-donating or an electron-withdrawing group at the 2-, 3-, or 4-position on the aryl moiety, linear or branched 1-aryl aliphatic alcohols, aryl furyl methanols, 1-aryl allylic alcohols, and, especially, 1-aryl propargylic alcohols in excellent enantioselectivities of >/=90% ee, except for the case of 1-naphthyl addition to benzaldehyde. Noteworthily, diarylmethanols in both R- and S-configurations can be obtained.     

Enantioselective rhodium-catalyzed addition of arylboronic acids to aldehydes using chiral spiro monophosphite ligands

[reaction: see text] Highly efficient rhodium-catalyzed asymmetric addition of arylboronic acids to aldehydes has been realized by using chiral spiro monophosphite ligands, affording diarylmethanols in excellent yields and good enantiomeric excesses.     

Me3Ga-mediated alkynylation of aldehydes

The trimethylgallium reagent was found to promote the addition of phenylacetylene to various aromatic and aliphatic aldehydes. This reaction was efficiently carried out in anhydrous CH₂Cl₂ at room temperature under mild conditions and the corresponding propargylic alcohols were obtained in good to excellent yields up to 98%.     

CoI-Catalyzed Barbier Reactions of Aromatic Halides with Aromatic Aldehydes and Imines

The reductive Barbier coupling of aromatic halides and electrophiles has been achieved using a CoBr₂/1,10-phenanthroline catalytic system and over stoichiometric amounts of zinc. The reaction displayed a broad scope of substrates, including (hetero)aryl chlorides as pro-nucleophiles and aldehydes or imines as electrophiles, leading to diarylmethanols and diarylmethylamines in moderate to excellent yields, respectively.     

CF3CO2ZnEt-mediated highly regioselective rearrangement of bromohydrins to aldehydes

A highly efficient and selective rearrangement reaction of bromohydrins to aldehydes mediated by CF₃CO₂ZnEt was described. The secondary and tertiary aldehydes were prepared under mild conditions in good to excellent yields (85-99%). The scope and limitations of this rearrangement process were also investigated.     

Highly enantioselective phenyl transfer to aryl aldehydes catalyzed by easily accessible chiral tertiary aminonaphthol

A new chiral tertiary aminonaphthol ligand 3b served as a highly efficient ligand for the asymmetric catalytic phenyl transfer to aromatic aldehydes and a variety of chiral diarylmethanols was prepared in high ee values (ee up to 99%) and chemical yields. The straightforward syntheses of both 3b and its enantiomer provide an excellent opportunity for large-scale applications.     

Radical mediated-direct conversion of aldehydes into acid bromides

A method of preparing acid bromides directly from aldehydes with Br₃CCO₂Et under radical conditions was developed. Aromatic aldehydes with electron-donating group were found to be more reactive than aromatic aldehydes with electron-withdrawing group and aliphatic aldehydes under reaction conditions.     

Planar chiral imidazolium salts based on [2.2]paracyclophane in the asymmetric rhodium-catalyzed 1,2-addition of arylboronic acids to aldehydes

A series of planar chiral imidazolium salts derived from [2.2]paracyclophane have been synthesized and characterized. By using these imidazolium salts as carbene precursors, the Rh-catalyzed 1,2-addition of arylboronic acids to aldehydes proceeded readily with low catalyst loadings (0.03–0.3 mol %) and gave a variety of chiral diarylmethanols in excellent yields and moderate enantioselectivities.     

One-pot synthesis of conjugated alkynenitriles from aldehydes

A method of preparing conjugated alkynenitriles was developed from various aldehydes with CCl₃CN and PPh₃ in the presence of ^tBuLi. The reaction proceeded via α-chlorovinyl nitrile as an intermediate without any side reactions such as chlorination of starting aldehydes.     

Enantioselective phenylacetylene addition to aldehydes induced by Cinchona alkaloids

Enantioselective addition of phenylacetylene to various aldehydes was studied in the presence of inexpensive and commercially available Cinchona alkaloids. A maximum of 85% ee was obtained using cinchonidine in the presence of Ti(OⁱPr)₄.