Recent Advances in the Synthesis of Diphenylmethyl Ethers

One-pot expeditious synthesis of glycosylated esters through activation of carboxylic acids using trichloroacetonitrile

Acetimidates, a valuable intermediate has been well explored as versatile synthon in a number of organic transformations particularly as suitable donors in glycosylation reactions. Herein, we explored acetimidates to furnish high-to-excellent yield of diverse glycosylated esters under one-pot mild reaction condition. The commercially available trichloroacetonitrile is implemented for the activation of carboxylic acid via in situ generation of trichloroacetimidate, which was subsequently attacked by sugar alcohols to deliver high-to-excellent yields of desired glycosylated esters. The devised method has some notable features such as metal-free condition, one-pot mild reaction condition, easy-handling, high-to-excellent yields, and broad substrate scope.

Organosulphur and organoselenium compounds as emerging building blocks for catalytic systems for O-arylation of phenols, a C-O coupling reaction

Diaryl ethers form an important class of organic compounds. The classic copper-mediated Ullmann diaryl ether synthesis has been known for many years and involves the coupling of phenols with aryl halides. However, the use of high reaction temperature, high catalyst loading and expensive ligands has created a need for the development of alternative catalytic systems. In the recent past, organosulphur and organoselenium compounds have been used as building blocks for developing homogeneous, heterogeneous and nanocatalysts for this C-O coupling reaction. Homogeneous catalytic systems include preformed complexes of metals with organosulphur and organoselenium ligands. The performance of such complexes is influenced dramatically by the nature of the chalcogen (S or Se) donor site of the ligand. Nanocatalytic systems (including Pd₁₇Se₁₅, Pd₁₆S₇ and Cu_1.8S) have been designed using a single-source precursor route. Heterogeneous catalytic systems contain either metal (Cu or Pd) or metal chalcogenides (Pd₁₇Se₁₅ or Cu_1.8S) as catalytically active species. This article aims to cover the simple and straightforward methodologies and approaches that are adopted for developing catalytically relevant organosulfur and organoselenium ligands, their homogeneous metal complexes, heterogeneous and nanocatalysts. The effects of chalcogen (S or Se) donor, halogen (Cl/Br/I) of aryl halide, nature (electron withdrawing or electron donating) of substituents present on the aromatic ring of aryl halides or substituted phenols and position (ortho or para) of substitution on the results of catalytic reactions have been critically analyzed and summarized. The effect of composition (Pd₁₇Se₁₅ or Pd₁₆S₇) on the performance of nanocatalytic systems is also highlighted. Substrate scope has also been discussed in all three types of catalysis. The superiority of heterogeneous catalytic systems (e.g., Pd₁₇Se₁₅ immobilised on graphene oxide) indicates the bright future possibilities for the development of efficient catalytic systems using similar or tailored ligands for this reaction.

Practical preparation of diphenylmethyl ethers from 2-diphenylmethoxypyridine using catalytic iron(iii) chloride

A novel facile synthetic method for producing diphenylmethyl (DPM) ethers from 2-diphenylmethoxypyridine was developed. A variety of DPM ethers was successfully achieved with high yield via treatment of alcohols with 2-diphenylmethoxypyridine in the presence of catalytic FeCl3. The procedure is a practical and efficient synthetic procedure to protect various alcohols, and it can be applied to prepare bioactive compounds.

Ester Formation via Symbiotic Activation Utilizing Trichloroacetimidate Electrophiles

Trichloroacetimidates are useful reagents for the synthesis of esters under mild conditions that do not require an exogenous promoter. These conditions avoid the undesired decomposition of substrates with sensitive functional groups that are often observed with the use of strong Lewis or Brønsted acids. With heating, these reactions have been extended to benzyl esters without electron-donating groups. These inexpensive and convenient methods should find application in the formation of esters in complex substrates.

Formation of DPM ethers using O-diphenylmethyl trichloroacetimidate under thermal conditions

Alcohols are effectively converted to their corresponding diphenylmethyl (DPM) ethers by reaction with O-diphenylmethyl trichloroacetimidate in refluxing toluene without the requirement of a catalyst or other additives. A number of acid and base sensitive substrates were protected in excellent yield using this new method without disturbing the pre-existing functionality present in these molecules. This reaction is the first example of the formation of an ether from stoichiometric amounts of a trichloroacetimidate and an alcohol without the addition of a Brønsted or Lewis acid catalyst.