Additives catalysis

Due to many impressive advances in metal-catalyzed transformations, both asymmetric and non-asymmetric, several efforts have been directed towards designing total synthesis routes that very heavily depend on various catalytic methods. These total syntheses benefit from the economic efficiency and environmental consciousness that are two of the inherent attributes of catalytic reactions. The total synthesis of wodeshiol 133 by Corey, discussed above (Scheme 19) is one such example. Two additional catalysis-based enantioselective total syntheses are briefly discussed below. In both efforts, all centers of asymmetiy are attained by a catalytic enantioselective method, and the synthesis is completed through the use of several other catalytic reactions. 

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Keywords Addition Catalysis Cross-coupling Cyclization Electron transfer Radicals Transition metals... 

Schmitz, A. and C. Song. Shape-Selective Isopropylation of Naphthalene over Dealuminated Mordenites. Enhancing p,(3-Selectivity by Water Addition. Catalysis Letters, 1996b, 40(1), 59-65. 

Ring-closure of Ce. The reaction of (13) with LDA led to a 2,4-diamino-thiophen, which according to n.m.r. exists in the imino-form (14). Compounds of type (14a), prepared by the condensation of methyl aryl ketones with phenyl isothiocyanates in the presence of sodium hydroxide followed by alkylation, gave the aminothiophens (14b) if is COPH or COMe, without additional catalysis by a base. On the other hand, if R is C02Et or CONH2, the thiazolidones (14c) were obtained and if R is CH2Br, (14d) was the product. 

The presence of metal ions in solution can have pronounced effects on the reactivity of phosphate esters. In addition, catalysis of reactions of phosphates by enzymes often involves metal ions. In an earlier review (Kluger, 1978), some of the possible modes of catalysis by metal ions were presented in terms of what was known of available hydrolytic mechanisms. 

By heating the monomer at 70 C in a pressure reactor vessel, self-condensation occurs and hydrogen is evolved. This reaction proceeds in a very easy, controlled manner without the need for additional catalysis. 

Grace, J.R., Li, X. and Lim, C.J. (2001) Equilibrium modelling of catalytic steam reforming of methane in membrane reactors with oxygen addition. Catalysis Today, 64, 141-149. 

Hn, X., Ln, G. (2010b). Acetic acid steam reforming to hydrogen over Co—Ce/A Os and Co—La/Al203 catalysts—the promotion effect of Ce and La addition. Catalysis Communications, 12, 50—53. 

In the aprotic systems, molecular oxygen can attack the dianion to form a peroxide and additional catalysis is not required for chemiluminescence. 

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