Reactions Catalyzed by f-Block Metal Alkoxides

The actinides and lanthanides or f-block metal alkoxides are the last group. According to the report of Nawaratna and co-workers, yttrium isopro-poxide has been catalyzed transesterification reaction of fatty acids (reaction 7.13) [78]. Hatano et al. have used this strategy in the presence of lanthanum alkoxides for transestrification of carboxylic esters and preparation of new esters [79]. 

Yukawa et al. used lanthanum isopropoxide/BINOL system, 128, for the catalysis of asymmetric aza-Morita-Baylis-Hillman reaction (reaction 7.28), in which the electron-deficient alkenes, 129, reacted with 

In deduction, it should be notified another time that working with meal alkoxide in large scale for industrial utilities may be completely different from bench scale at laboratory. All of these researches would be scaled up carefully to show their limitations. Of course some difficulties maybe overcame very simply as hydrolyzing which Berkessel et al. solved it by scaling up the reaction [45]. But there are some problems that did not expose until the reaction is done in large scale. 

From this short survey, it should become clear that metal alkoxide, beside their working considerations, have very large prospective applicability in different area of organic reaction catalysis which must be investigate more comprehensively to show their properties more clearly. Steric and electronic possessions have crucial effect on catalytic properties of metal alkoxides like many other metal complexes. In one hand, electronic properties of different substituents on alkyl R group of metal alkoxides determine their metal core Lewis acidic property and/or Lewis basic character of alkoxy oxygen atom which both have substantial effect on their catalytic behavior. In addition, steric properties of alkyl R group may hinder substrate to come closer or to attack by active site of catalyst. 

Other challenges not only in metal alkoxide catalysis but in catalytic processes generally are development of catalytic protocols which on one hand could work in solvent free condition or in green solvent such as water or liquid CO, and on the other, could recover without loss of its activity. Supporting metal alkoxide onto the inorganic solids [47,49, 50] especially magnetic ones [38] can effectively solve the later one. Reported results (Tables 7.1-7.4) are also showed that in most cases solvent free conditions made products with better properties especially in the catalytic polymerization processes. In these processes, coordinative solvents drastically reduced the quality of product because they competed with monomer to coordinate to the metal core. This step is the basic process in coordination-insertion mechanism in ROP reactions [4, 11, 31, 54]. 

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