Palladium-catalyzed arylation of aldehydes with bromo-substituted 1,3-diaryl-imidazoline carbene ligand

Total Synthesis of Linear Coumarniolignoids (+) and (-)-Sapiumin C, (-)-Moluccanin, and (-)-Hemidesminine

Coumarinolignoids (CLs) are a class of natural products isolated from a diverse range of plant species. Due to their unique structural scaffold, they exhibit a wide range of interesting biological activities including hepatoprotective, antitumor, anti-inflammatory, and antioxidant activities among others. In this research, key intermediate 10 was used to stereoselectively synthesize CLs (7'S,8'S)- and (7'R,8'R)-sapiumin C 1 and 2, (7'S,8'S)-moluccanin 3, and (7'S,8'S) hemidesminine 4 for the first time, establishing a versatile synthetic method for the stereoselective synthesis of linear CLs. The developed method includes a Mitsunobu coupling, a modified Miyaura arylation via a rhodium catalyst, and an acid-catalyzed cyclization in key bond-forming steps. The developed synthetic route allows the synthesis of both enantiomers of a given natural product from the same chiral pool reagent (S)-solketal while allowing easy variation of aromatic substitution and hydroxymethyl/allylhydroxymethyl moieties that are common in this class of natural products.

Pd-Catalyzed cross-coupling synthesis of 4-aryl-3-formylcoumarins

The threefold cross-coupling of triarylbismuth reagents with 4-chloro-3-formylcoumarins furnished the corresponding 4-aryl-3-formylcoumarins in a chemoselective manner with high yields under Pd-catalyzed conditions. This method was successfully applied to electronically different triarylbismuth reagents and 4-chloro-3-formylcoumarins preserving the 3-formyl group in the coumarin scaffold.

Transition Metal Catalyst-Free, Base-Promoted 1,2-Additions of Polyfluorophenylboronates to Aldehydes and Ketones

A novel protocol for the transition metal-free 1,2-addition of polyfluoroaryl boronate esters to aldehydes and ketones is reported, which provides secondary alcohols, tertiary alcohols, and ketones. Control experiments and DFT calculations indicate that both the ortho-F substituents on the polyfluorophenyl boronates and the counterion K+ in the carbonate base are critical. The distinguishing features of this procedure include the employment of commercially available starting materials and the broad scope of the reaction with a wide variety of carbonyl compounds giving moderate to excellent yields. Intriguing structural features involving O-H⋅⋅⋅O and O-H⋅⋅⋅N hydrogen bonding, as well as arene-perfluoroarene interactions, in this series of racemic polyfluoroaryl carbinols have also been addressed.

Generation of Aryllithium Reagents from N-Arylpyrroles Using Lithium

Treatment of 1-aryl-2,5-diphenylpyrroles with lithium powder in tetrahydrofuran at 0 °C results in the generation of the corresponding aryllithium reagents through reductive C–N bond cleavage.

Tandem addition/cyclization for synthesis of 2-aroyl benzofurans and 2-aroyl indoles by carbopalladation of nitriles

Pd-Catalyzed tandem reaction of 2-(2-acylphenoxy)acetonitriles or 2-((2-benzoylphenyl)amino)acetonitrile with arylboronic acids for the synthesis of 2-aroyl benzofurans and 2-aroyl indoles.

Ir(COD)Cl]2/Tris(2,4-di-t-butylphenyl)phosphite-Catalyzed Addition Reactions of Arylboronic Acids with Aldehydes

[Ir(COD)Cl]2/tris(2,4-di-t-butylphenyl)phosphite-catalyzed addition reactions of arylboronic acids with aldehydes were described. The Ir(I) catalyst, generated from [Ir(COD)Cl]2 and tris(2,4-di-t-butylphenyl)phosphite, was an efficient catalyst system for the addition reactions of a variety of arylboronic acids with aromatic and aliphatic aldehydes. The easy availability of the catalyst and good yields make these reactions potentially useful in organic synthesis.