TiCl4, heat treatment with

Synthesis of the third-generation catalyst is an intricate process. Two crucial steps are (1) Precipitation of the supported catalyst from a solution of Mg2+ ion in organic solvent by the addition of TiCl4. (2) Catalyst activation by heat treatment with TiCl4 and phthalate esters (third component). The precursors for the support could be magnesium alkoxides, carboxylates, sulhte, or sulfinates. They all give particles of different but well-defined morphologies. 

The various procedures for the synthesis of this system have previously been described. From now on, reference shall only be made to the preparation procedure requiring MgC co-milling with the Lewis base (generally EB), and subsequent heat treatment with TiCl4, followed by repeated washings with hydrocarbons in order to remove not bonded TiCl4. The main reasons for this choice are ... 

Sn[N(TMS)2l2, A, A -carbonyldiimidazole (110, p. 1418), which behaves as in reaction 16-63, POCl3, °" TiCl4, ° molecular sieves,Lawesson s reagent (p. 1278), ° and (MeO)2POCl. ° Certain dicarboxylic acids form amides simply on treatment with primary aromatic amines. In these cases, the cyclic anhydride is an intermediate and is the species actually attacked by the amine. Carboxylic acids can also be converted to amides by heating with amides of carboxylic acids (exchange),sulfonic acids, or phosphoric acids, for example, ... 

Carbon-coated Ti02 was also prepared from TiCl4 with fructose mixed in benzyl alcohol by heat treatment at 300 to 900°C in vacuum [299]. 

A second generation was developed in the 1970s. It was found that ether extraction of the brown precipitate to remove AICI3 followed by heat treatment at 60°C-100°C in the presence of excess TiCl4 gave a catalyst with smaller, more active crystallites. 

Silica-supported Lewis acids are useful catalysts with microwave irradiation for conjugate additions. The silica-supported catalysts are obtained by treatment of silica with ZnCh [Si(Zn)], Et2AlCl [Si(Al)] or TiCl4 [Si(Ti)] [ 150-152], The Michael addition of methyl a-acetamidoacrylate (196) with indole (2) under Si(M) heterogeneous catalysis assisted by microwave irradiation afforded the alanine derivative 197 within 15 min and/or bis-indolyl 198, depending on the reaction conditions (Scheme 45) [153]. While the bis-indolyl product 198 is only formed when Si(Zn) was used as catalyst, the alanine derivative 197, as a single product is formed under thermal heating in a yield of 12%. The best yields were observed with Si(Al) (Table 5). The product 198 was obtained by elimination of acetamide followed by a-Michael addition between intermediate 199 with a second mole of indole. 

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