Selective catalytic reagents

Prefer selective catalytic reagents over stoichiometric reagents... 

Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. 

Currently, production of eflornithine has been stopped because of industrial policy and environmental problems it involves the use of Ereon (CHF2CI) as a reagent in its synthesis (Eigure 8.27). However, production of eflornithine may start again in order to supply the WHO. Another reason is that a topical formulation for the treatment of female hirsutism has recently been launched (Vaniqa). Its synthesis has recently been improved by using the selective catalytic reduction of the cyano group without any cyclization into lactam. ... 

Nanocrystalline MgO and CaO with high surface area are able to absorb large amounts of chlorine, which undergo dissociative chemisorption. These can serve as rather selective, catalytic alkane chlorination reagents, which suggests that trapped Cl atoms are involved in the reaction.295 Liquid-phase low-temperature chlorination of alkanes is also possible in the presence of various alkenes as inductors and AIBN [azobis(isobutyronitrile)] 296... 

Alkyl and aryl sulfides RSH react with equimolecular amounts of p-toluenesulfonyl-acetylene, HC C-SC Tol, in CH3CN at 0 °C or room temperature in the absence of any catalytic reagent to give Z-adducts RS-CH=CH-S02Tol with total diastereo-selectivity. On the other hand, in the presence of 1.1 equiv. of NaH in THF, the same reaction affords the corresponding li-diastereoisomers also with total diastereoselec-tivity.211... 

The successful commercial use of TPPTS has triggered much research for other water-soluble phosphines. While some of these certainly give highly active and selective catalytic systems, as yet their cost of manufacturing make them commercially unattractive. For example, the fc-phosphine 5.14 gives a catalytic system that is about ten times more active than the one with TPPTS and also shows a higher selectivity (—98%) towards n-butyraldehyde. Its synthesis, however, is a five-step process and involves expensive reagents. 

Process for Selective Catalytic Oxidation of Olefins to Aldehydes, Ketones with Cleavage of C=C Bonds R.W. Fischer etaU US Patent 6,303,828 (October 16, 2001) Aventis Research Technologies and GmbH Co. KG Olefin Oxidizing Reagent... 

Since the type of difficulty that must be overcome to achieve a selective catalytic process depends on the types of substrates and reagents used, we shall describe the criteria adopted for each catalytic reaction. 

Catalysis Catalytic reagents (as selective as possible) are superior to stoichiometric reagents. (Many nanoscale catalysts exhibit improved selectivity and/or activity as compared to bulk systems.)... 

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