Lead isopropoxide, synthesis

GRUNDMANN ALDEHYDE SYNTHESIS. Transformation of an acid into an aldehyde of the same chain length by conversion of the acid chloride via the diazo ketone to the acetoxy ketone, reduction with aluminum isopropoxide and hydrolysis to the glycol, and cleavage with lead tetraacetate. 

In conclusion it is necessary to note the considerable change in chemical activity occurring on transformation from the alkoxides into oxocomplexes. An example is the synthesis of a bimetallic Bi-Ti complex. The complex formation of 2 isopropoxides occurs only in the presence of water (h = 0.2-0.7), which leads to the formation of Bi-oxoisopropoxide, which then reacts with Ti(OPr )4 already at room temperature providing BiTi20(0Pr% [447] (see also Chapter 8). Teyssie et al. [760] have proposed a large group of alkoxides of 3d-transition metals, and also those of Zn, Al, and Mo as highly effective selective catalysts for polymerization of lactones, isocyanates, and so on. 

The formation of this double alkoxide further complicates the precursor chemistry involved in the synthesis. Since Y and A1 isopropoxides are initially mixed in a ratio corresponding to the stoichiometry of YAG (3 5 = Y/Al), the reaction between the two alkoxides results in a solution containing a mixture of Y-Al double isopropoxide (1 3) and excess Y-isopropoxide. During hydrolysis, Y-isopropoxide hydrolyzes much faster than the double alkoxide, causing precipitation of Y-(OH) t to occur, which eventually leads to inhomogeneity in the final product. 

The ability of zeolites to adsorb and retain small molecules such as water forms the basis of their use in the noncatalytic synthesis of fine chemicals (Van Bekkum and Kouwenhoven, 1988, 1989). One of the best recent examples is the use of NaA zeolite in the Sharpless asymmetrical epoxidation of ally lie alcohols (see Chapter 10) (Gao et al., 1987 Antonioletti et al 1992). In this Ti(IV)-catalyzed epoxidation by t-butyl hydroperoxide in the presence of diethyl tartrate (reaction 6.4), it has been demonstrated that the inclusion of zeolites (3 A or 4 A) leads to high conversion (>95%) and high enantioselectivity (90-95% ee). The effect of the zeolite is quite dramatic. It is believed that the role of the zeolite is to protect the titanium isopropoxide catalyst from water, perhaps generated during the reaction. 

Teff D.J., Caulton K.G. Hydrolytic synthesis of lead oxo isopropoxides and their reaction with M(0 Pr)4 (M = Ti, Zr) Comparisons and contrasts. Inorg. Chem. 1998 37 2554... 

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