Nano TiO2 supported on SiO2 (Nano TiO2@SiO2) as a solid Lewis acid, was described to be an effective and reusable catalyst for one-pot three-component reaction of benzil, aryl aldehydes and ammonium acetate for the synthesis 2-aryl-4,5-diphenyl-1H-imdazoles synthesis. To explore the high efficacy of the catalytic system the four-component cyclization of benzil, aryl aldehydes, ammonium acetate ...

The intramolecular Schmidt reaction of ketones and tethered azides is an efficient method for the generation of amides and lactams. This reaction is catalyzed by Lewis acids, which tightly bind the strongly basic amide product and result in product inhibition. We report herein conditions to achieve a catalytic Schmidt reaction using substoichiometric amounts of the heat-stable Lewis acid Sc(OTf...

The reaction of levulinic acid production from glucose has a stage that requires high temperature and activation energy so in this catalyst is needed. required must have lewis site bronsted the acidity very influential for successful levulonic acid. Silica nickel phosphate catalysts sites Ni metal phosphoric silica groups. was measured using pyridine ammonia adsorption method center strength TG...

in this research we used heavy propylene tetramer (hpt) and a1c13 —bf3 (lewis acids) ascatalyst and ethanol, n-propanol and n-butanol as co-catalyst. using lewis acids as catalyst, thehpts form molecules with higher molecular weight. since the raw materials of the reaction are byproducts of other reactions, are not pure and contain various compounds with different m.w andalso different chemical...

The amplifying asymmetric autocatalysis discovered by Soai and coworkers in 1995 does not fit easily into the extensively investigated framework of organozinc alkylation of aldehydes. In that case the catalyst is a monomeric Zn chelate that functions as both Lewis acid and Lewis base, permitting the simultaneous coordination of both dialkylzinc reagent and aldehyde reactant. By contrast, the So...

A catalyst-free oxyboration reaction of alkynes is developed. The resulting borylated isocoumarins and 2-pyrones are isolated as boronic acids, pinacolboronate esters, or potassium organotrifluoroborate salts, providing a variety of bench-stable organoboron building blocks for downstream functionalization. This method has functional group compatibility, is scalable, and proceeds with readily av...

The adsorption of pyridine on a complete monolayer molybdenum oxide-Al203 catalyst was studied. Both Lewis and Bronsted acid sites are present on a catalyst with a Mo valence of -4.1. The orientation of adsorbed pyridine was studied by means of its interaction with surface OD groups, which leads to the formation of only 2-deuteriopyridine. The fraction of molybdenum ions active for hydrogenatio...

We report a mechanistically based study of bifunctional catalyst systems in which chiral nucleophiles work in conjunction with Lewis acids to produce beta-lactams in high chemical yield, diastereoselectivity, and enantioselectivity. Chiral cinchona alkaloid derivatives work best when paired with Lewis acids based on Al(III), Zn(II), Sc(III), and, most notably, In(III). Homogeneous bifunctional ...

A concise enantioselective synthesis of tetrahydrolipstatin (THL) and seven stereoisomers has been achieved. The synthesis of THL was accomplished in 10 steps and 31% overall yield from an achiral ynone. Key to the success of the approach is the use of a bimetallic [Lewis acid](+)[Co(CO)4](-) catalyst for a late-stage regioselective carbonylation of an enantiomerically pure cis-epoxide to a tra...