Caesium carbonate addition with

The syntheses of the receptors 10 and 12 were carried out by the treatment of bisphenol porphyrin 13 and its Zn complex 14, respectively, with portionwise addition of a large excess of P-cyclodextrin-6-O-monotosylate (CD-Tos) 15 using caesium carbonate as base in N,N dimethyl formamide (DMF) (Fig. 6) (13). 

Ccesium Niobates.—Fusion of niobium pentoxide and caesium carbonate and extraction of the melt with water yields monoclinic crystals which have the composition 4Cs20.3Nb205.14H20, and which are iso-morphous with the rubidium salt. Addition of alcohol to the aqueous solution furnishes crystals of 7Cs2O.6Nb2O5.80H2O. ... 

Caesium Tantalates.—Fusion of tantalum pentoxide with caesium carbonate and extraction with water yields monoclinic crystals of the 4 3 salt, 4Cs20.3Taa05.14H20 addition of alcohol to its aqueous solution precipitates the 7 6 salt, 7Cs20.6Ta205.38H20.4... 

Equip an oven-dried, three-necked round-bottomed flask with a magnetic stirrer bar, two pressure-equalising addition funnels (250 mL) and an air condenser attached to a nitrogen line. Add caesium carbonate (3.6 g, 11 mmol) and dry DMF (500 mL) to the flask heated to 55°C and prepare in each addition funnel solutions of 1,2-dibromoethane (1.83 g, 10 mmol) in DMF (200 mL) and / /-(toluenesulfonyl)-3-azapentane-1,5-dithiol (2.91 g, 10 mmol) in DMF (200 mL), respectively. 

Caesium sulphites.3—The normal sulphite, Cs2S03, is prepared by addition of an equivalent proportion of caesium carbonate to an alcoholic solution of the salt saturated with sulphur dioxide. It forms white, readily soluble crystals. 

Oxidative dimerisation of 4-methoxyphenol has been mentioned in the previous chapter. 4-Methylphenol in bromobenzene containing caesium carbonate, the only effective base for the reaction, was mixed with 10mole% of a rhodium complex at ambient temperature. Heating of the mixture at 90X for 24 hours afforded a 51% yield of the coupled product, 2,2 -dihydroxy-5,5 -dimethylbiphenyl (ref. 73). The yield was improved by the addition of 2.2 moles of water. 

Nucleophilic intramolecular addition of a carbon-silicon bond onto a carbon-nitrogen iminium ion is the key step of a berbine synthesis <82CC769,83H(20)417>. Thus, treatment of the isoquinolinium salt (235) with caesium fluoride in ethanol afforded (+)-xylopinine (237), presumably via the betaine (236) (Scheme 45). A silicon-directed intramolecular cyclization of a A-acyliminium ion (238) was also the key step of Speckamp s synthesis of (+)-epilupinine as shown in Scheme 46 <85JOC40I4>. 

---