Benzils: A Review on their Synthesis

Abstract

This review segregates and outlines all the aspects of the synthesis of Benzil for almost two centuries. Here, state of the art review includes the early synthesis in 1836 to the advancement made over the past years in the knowledge of the preparation of benzil derivatives till the present. Benzil is one of the important and highly underrated organic compounds in which two adjacent carbonyl groups are flanked by two phenyl rings. Apart from its diverse functionality, the reactivity of benzils proclaims its prospects as a reagent for the synthesis of various heterocycles. On recasting benzil, it is possible to obtain a wide variety of utilities in pharmaceuticals, polymer, and material chemistry. This contemplation of the review gives a general perspective of reaction routes, mechanisms and highlights the conversions due to oxidation, and accentuates benzil as an emerging putative target.

Iridium–phosphine ligand complexes as an alternative to rhodium-based catalysts for the efficient hydroformylation of propene

“…For the hydroformylation catalyzed by Rh-based complexes, the most widely utilized ligand is the phosphine compound (Scheme 1). 9–32 Hence, we mainly focused on the Ir-based catalysts with different monodentate and bidentate ligands. The phosphine ligands are listed in Scheme 2, including the following: triphenylphosphine ( L1 ), tri(4-methoxyphenyl)phosphine ( L2 ), diphenyl( n -propyl)phosphine ( L3 ), tri( n -butyl)phosphine ( L4 ), tri(3-pyridyl)phosphine ( L5 ), di(3-pyridyl)phenylphosphine ( L6 ), diphenyl(3-pyridyl)phosphine ( L7 ), tri(4-methoxypyridyl)phosphine ( L8 ), tri(4- N , N -dimethyl-pyridyl)phosphine ( L9 ); diphenylphosphinomethane ( L10 ), 1,3-bis(diphenylphosphino)propane ( L11 ), 1,4-bis(diphenylphosphino)butane ( L12 ), 1,5-bis(diphenylphosphino)pentane ( L13 ), 1,6-bis(diphenylphosphino)hexane ( L14 ), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene ( L15 ), and tris(2-pyridyl)phosphine ( L16 ).…”

“…Since Rh-based catalysts were applied to olefin hydroformylation by Evans et al , 8 the research on Rh-based catalysts for the hydroformylation of olefin has achieved great progress. 9–34 Compared to the first-generation Co-based catalysts, which typically operate at reaction temperatures of up to 160 °C and under high reaction pressure of 10 MPa, 35,36 and Ru-based catalysts with low activity and poor selectivity for aldehydes, 37,38 Rh-based catalysts have incomparable advantages in olefin hydroformylation, such as mild reaction conditions (80–120 °C and below 3 MPa) and high selectivity for aldehydes (>98%). 19,39–45 Consequently, a significant number of research studies have been directed towards the modification of Rh catalysts.…”

Metal-free, 2-MeTHF mediated C(sp)–H functionalization of alkynes with anilines to access diaryl 1,2-diketones bearing lowerE-factors

“…Due to their widespread applications, numerous methods have been developed for the synthesis of α-diketones with increasing interest in the recent decade. 8 Regarding this, the alkyne system has proved to be a promising choice in alternative oxidative reactions and C(sp)–H has given rise to a huge initiative toward functionalized transformations. These oxidation strategies promote the coupling of internal or terminal alkynes with various formal reaction partners such as aryl iodide (–I), hydrazine (–NHNH 2 ), trifluoromethanesulfonate (–OTf), and boronic acid to afford α-diketones.…”

Titanium-Mediated C–C Coupling of Imidoylstannanes for the Synthesis of Tetraaryl Diimines. Isolation of Titanium Iminoacyl and Ene-diamido Intermediates

“…In addition, tetraaryl-substituted α-diimines with bulky aryl groups on the nitrogen atoms, which are widely used in metal-catalyzed reactions, could not be prepared by the coupling reactions. Nevertheless, the condensation of diphenyl-1,2-diones with bulky aryl amines mediated by Lewis acids have been reported to yield the corresponding tetraaryl-substituted α-diimines. , More recently, titanium imido mediated multicomponent reactions of alkynes and C-nitrosos have been reported for the synthesis of various C-substituted diimines…”

“…Stirring a mixture of 1a with 1 equiv of TiCl 4 in refluxing n -hexane led to the formation of the η 2 -iminoacyl titanium trichloride 3 in high yield (Scheme ). Complex 3 represents the first example of an η 2 -iminoacyl titanium trichloride, although several η 2 -iminoacyl titanium complexes supported by organic ligands have been previously prepared by the insertion of isocyanide into a titanium–alkyl bond . Complex 3 has been fully characterized by spectroscopic methods and X-ray single-crystal diffraction studies.…”