Grignard reagents/cerium chloride

The Grignard reagent/cerium chloride system has been applied to practical organic syntheses. A typical example is shown in Scheme 27. In sharp contrast to the reaction in the presence of cerium cUoride, the Grignard reagent alone affords only a 2% yield of the adduct. 

CARBONYL ADDITIONS, CERIUM(III) CHLORIDE-PROMOTED, 76, 237 Carbonyl compounds, reactions with organolithiums or Grignard reagents, 76, 228 Carboxylic acid amides, 77, 27 Cells, storage of, 76, 80 Centrifugation, 76, 78... 

The addition reactions are usually carried out at -78 °C, except for reactions of the Grignard re-agent/cerium chloride system (Section 1.8.4), which are conducted at 0 °C. A substrate is added to the well-stirred organocerium reagent and the mixture is stirred until the reaction is complete. Work-up is carried out in the usual manner quenching with dilute HCl or dilute AcOH and extraction with a suitable organic solvent. When the substrates are acid sensitive, work-up using tetramethylenediamine is recommended. ... 

Table 5 Reactions of Carbonyl Compounds with Grignard Reagents in the Presence of Cerium Chloride or with Grignard Reagents Alone ... 

Representative examples of the reactions of various carbonyl compounds with Grignard reagents under these conditions are listed in Table 5. It is emphasized that enolization, aldol reaction, ester condensation, reduction and 1,4-addition are remarkably suppressed by the use of cerium chloride. Various tertiary alcohols, which are difficult to prepare by the conventional Grignard reaction, can be synthesized by this method. 

USE OF CERIUM(III) CHLORIDE IN THE REACTIONS OF CARBONYL COMPOUNDS WITH ORGANOLITHIUMS OR GRIGNARD REAGENTS FOR THE SUPPRESSION OF ABNORMAL REACTIONS ... 

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