Synthesis of diaryl ethers based on one-pot [3+3] cyclizations of 1,3-bis(silyl enol ethers)

Functionalized and sterically encumbered diaryl ethers were prepared by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 2-aryloxy-3-(silyloxy)alk-2-en-1-ones.     

Nucleophilic Addition of Ytterbium Metal Umpoled Diaryl Ketones to Imines

Abstract

Cross-coupling reactions of diaryl ketones with imines promoted by ytterbium metal were described. β-Amino alcohols were prepared in good yields under mild and neutral conditions.     

A simple and efficient synthesis of new cyclic ureas

A facile access to a wide range of original saturated N-heterocyclic ureas is described using, as a key step, a Michael-type reaction involving isocyanates or amines on a piperidine framework possessing an α,β-unsaturated ester functionality.     

Critical view on the recent enantioselective synthesis of alcohols,amines and related molecules having tertiary benzylic stereocenter

Stereochemically defined enantioenriched molecules were, are and will always be playing a pivotal role in the development of novel pharmaceutical agents. On this line, compounds having tertiary benzylic stereocenter are of special note. This has led to an increase in the development of novel synthetic strategies for accessing molecules having this structural moiety. The current critical discussion proposes to describe the various synthetic methodologies for the enantioselective synthesis of diaryl methanols, diarylmethyl amines and other related scaffolds with tertiary benzylic stereogenic center that came up during 1995–2016. Through this critical view, we would not only like to give the readers a brief outlook on the different techniques that can be followed for the synthesis of a vast array of entities having this structural core, but also would like to highlight the limitations the protocols that need to be addressed.     

Molecular modelling of some para-substituted aryl methyl telluride and diaryl telluride antioxidants

Quantum mechanical calculations using the 3-21G(d) basis-set were performed on some p-substituted diaryl tellurides and aryl methyl tellurides, and the corresponding cationic radicals of these compounds. Calculated relative radical stabilization energies (RSE:s) were shown to correlate with experimentally determined peak oxidation potentials (R=0.93) and ¹²⁵Te-NMR chemical shifts (R=0.91). A good correlation was also observed between the RSE:s and the Mulliken charge at the tellurium atoms (R=0.97). The results showed that Hartree–Fock calculations using the 3-21G(d) basis set was sufficiently accurate for estimating the impact of p-substituents in aryl tellurides on experimentally determined properties such as peak oxidation potentials and ¹²⁵Te-NMR chemical shifts.     

Convenient Stille carbonylative cross-couplings using molybdenum hexacarbonyl

Palladium catalysis was used in Stille-type carbonylative cross-couplings employing Mo(CO)₆ as the carbon monoxide source. Robust and convenient transformations were carried out in closed vessels at 100 °C, providing a set of diaryl ketones in good yields. Aryl triflates and bromides were used as coupling partners with aryl stannanes. Inclusion of the Mo(CO)₆ destabilizing agent DBU made this protocol operationally simple and suppressed side-product formation.     

A total synthesis of verbenachalcone, a bioactive diaryl ether from Verbena littoralis

Verbenachalcone 1, isolated from the aerial part of Verbena littoralis H. B. K. (Verbenaceae), has successfully been synthesized by employing anodic oxidation of the phenol derivative 3, as the key step. The bromine and chlorine substituents of 3 effected regioselective introduction of a methoxy group, as well as modulating the oxidation reaction. A flow-cell type apparatus of anodic oxidation provided the desired diaryl ether 4 in good yield.     

The enthalpies of interaction of glycine with some amides and ureas in water at 25°C

Measurement of solution enthalpyiesof glycine in aqueous solutions of formamide (F), N-methylformamide (NMF), N,N-dimethylformamide (DMF), monomethylurea (MMU), 1,3-diethylurea (DEU) and tetramethylurea (TMU) at 25°C have been undertaken. On the basis of the results, enthalpic coefficients of heterotactic interactions between a glycine zwitterion and a molecule of organic substance in aqueous solutions have been calculated. Using the additivity of groups concept by Savage and Wood (SWAG), contributions of each functional group of studied amides and ureas have been estimated. In this model a zwitterion of glycine has been considered as an individual equal to a single functional group.     

Cu-nanoparticle catalyzed O-arylation of phenols with aryl halides via Ullmann coupling

Recyclable Cu-nanoparticles provide an efficient, economic, and novel method for the synthesis of diaryl ethers via Ullmann type coupling. This method provides a wide range of substrate applicability and avoids the use of a heavy metal co-catalyst and gives diaryl ethers in satisfactory yields.