A very efficient one-pot three-component synthesis of pyran derivatives has been improved by condensation of aldehydes and malononitrile with dimedone under 80 °C using sucrose as natural and biodegradable catalyst in water. This method offers some advantages including inexpensive, high to quantitative yields, short reaction time, and easy work-up. Therefore, this methodology is entirely g...

The total synthesis of the recently reported marine natural product colombiasin A (1) and determination of its absolute configuration are reported. Two Diels-Alder cycloadditions and a palladium-catalyzed rearrangement are employed as key reactions to construct the tetracyclic framework of the target molecule. The enantioselective synthesis of colombiasin A utilizes Mikami's [(S)-BINOL-TiCl2] c...

The discovery of new strategies that emulate nature!s capacity to rapidly construct architectural complexity continues to be a central focus for research and development in the chemical sciences. Recently, our laboratory disclosed the concept of organocascade catalysis, a new chemical paradigm that combines two modes of catalyst activation (iminium and enamine catalysis) into one mechanism, the...

A palladium-catalyzed cascade carbonylative spirolactonization of hydroxycyclopropanols has been developed to efficiently synthesize oxaspirolactones common to many complex natural products of important therapeutic value. The mild reaction conditions, high atom economy, broad substrate scope, and scalability of this new method were highlighted in expedient total syntheses of the Turkish tobacco...

poly (n-bromosuccinimide) (pnbs) as a mild, efficient, non-acidic, polymeric and heterogeneous catalyst was applied for simple conversion of epoxides into thiiranes by treatment with kscn or (nh2)2cs at room temperature. aliphatic and aromatic epoxides converted into their corresponding thiiranes under mild conditions. all reactions proceeded in short reaction times and afforded the correspondi...

Deactivation of cobalt and nickel catalysts in Fischer-Tropsch synthesis and methanation JAVIER BARRIENTOS Akademisk avhandling som med tillstånd av KTH i Stockholm framlägges till offentlig granskning för avläggande av teknologie doktorsexamen fredagen den 23 september kl. " True wisdom comes to each of us when we realize how little we understand about life, ourselves, and the world around us....

C media, particularly blogs, can help companies increase the visibility of their products without spending millions of dollars in advertising. Although a number of companies realize the potential of blogs and encourage their employees to blog, a good chunk of them are skeptical about losing control over this new media. Companies fear that employees may write negative things about them and that ...

The photocatalytic decomposition of 2-, 3and 4-chlorobenzoic acids (2CB, 3CB and 4CB, respectively) with TiO2 loaded on HZSM-11 zeolite was investigated. The optimum decomposition rate of 2CB was obtained with TiO2/HZSM-11(30%) (TiO2 30 wt.%) catalyst at a concentration of 1 mg mL. 2CB and 3CB decompose at similar rates, but 4CB remains adsorbed on TiO2/HZSM-11(30%) without further degradation....