Transesterification for Synthesis of Carboxylates Using Aldehydes as Acyl Donors via C–H and C–O Bond Activations

Synthesis of N-Hydroxysuccinimide Esters, N-Acylsaccharins, and Activated Esters from Carboxylic Acids Using I2/PPh3

A method for the syntheses of isolable, active esters is described in which carboxylic acids are treated with triphenylphosphine, iodine, and triethylamine. Active esters accessible in this way include N-hydroxysuccinimide esters, N-hydroxyphthalimide esters (N-(acyloxy)phthalimides), N-acylsaccharins, pentafluorophenol esters, pentachlorophenol esters, N-hydroxybenzotriazole esters, and hexafluoro-2-propanol esters. The approach can be similarly applied toward the formation of N-acylsaccharins and N-acylimidazoles. The method is suitable for the formation of isolable active esters of aromatic and aliphatic activated acids as well as α-amino acid derivatives. These products are widely used reagents in organic synthesis, peptide synthesis, medicinal chemistry, and chemical biology (e.g., for bioconjugations). The method has broad substrate scope, uses simple and inexpensive reagents, avoids the use of carbodiimides or other coupling agents, and occurs at room temperature. Additionally, the diastereomers of compound Boc-Ala-NHCHPh are demonstrated to be distinguishable by 1H NMR (in DMSO-d6), allowing for a straightforward NMR method to establish the degree of racemization of activated esters of Boc-Ala or amide bond formations using Boc-Ala.

Mesoporous Carbon-Supported Pd Nanoparticles in the Metallic State-Catalyzed Acylation of Amides with Aryl Esters via C-O Activation

Carbon, an abundant, inexpensive, and nonmetallic material, is an inimitable support in heterogeneous catalysis, and variable carbonaceous materials have been utilized to support metal nanoparticle catalysts. We developed an efficient and stable heterogeneous catalyst with highly dispersed metallic palladium nanoparticles embedded in an ordered pore channel of mesoporous carbon and first applied the catalyst to construct imides from amides using aryl esters as an acylation reagent via C-O activation. The catalyst represents excellent catalytic performance and could be reused and recycled five times without any significant decrease in activity. The heterogeneous nature of metallic state palladium was proven to be the active center in the acylation reaction.

Formation of 1-Hydroxymethylene-1,1-bisphosphinates through the Addition of a Silylated Phosphonite on Various Trivalent Derivatives

An easily handled one-pot synthetic procedure was previously developed for the synthesis of bisphosphinates starting from acyl chlorides. Herein, other trivalent derivatives as acid anhydrides and activated esters were tested to form various bisphosphinates. This modulation of the reactivity can be controlled according to the nature of the acid derivative for the use of sensitive and functionalized substrates.

K2CO3-promoted formation of aryl esters from primary aryl amides by the acyl-acyl exchange process

A new acyl-acyl exchange reaction has been developed for the formation of aryl esters from primary aryl amides. The reaction could occur under mild reaction conditions with catalytic quantities of K2CO3, and could afford moderate to good yields of the desired products.

One pot synthesis of diarylfurans from aryl esters and PhI(OAc)2 via palladium-associated iodonium ylides

The example of palladium-catalyzed intermolecular cyclization for the synthesis of various diarylfurans in which one of the aromatic rings originates from the phenolic part of the starting ester and the other one from PhI(OAc)2 has been reported. The reaction is carried out through two steps: the rearrangement of palladium-associated iodonium ylides to form o-iodo diaryl ether and then palladium catalyzed intramolecular direct arylation. This reaction can tolerate a variety of functional groups and is alternative or complementary to the previous methods for the synthesis of diarylfurans.