Caesium carbonate

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). 

Mesomalonodialdehyde 1,3-dioxime is treated with arylhydrazines to give the mesoaldehyde 1,3-dioxime-2-arylhydrazones (685), which are O-acetylated with acetic anhydride to afford the mono-and di-acetyl derivatives (Scheme 139). Both intermediates are cyclized to 2-aryl-1,2,3-triazole-4-carbaldehyde oximes (686) and (687) with caesium carbonate. Triazoles (687) are converted to 4-cyanotriazoles by refluxing with acetic anhydride followed by pyrolysis <83JHC1561>. 

A reaction of sulfoximine 268 with ort o-substituted halobenzaldehydes 269 takes place in the presence of a catalytic amount of Pd(ii), 2,2 -bis(diphenylphosphanyl)-l,l -binaphthyl (BINAP), and caesium carbonate at 110°C to afford fully conjugated 2-phenyl-2,l-benzothiazine 2-oxides 270 with a S(vi) oxidation state (Scheme 38) <1999AGE2419>. Bis-benzothiazine 75 has been prepared from dibromo-dialdehyde 271 in a similar manner and investigated as a ligand for Pd-catalyzed allylic alkylation reactions (see Section 8.07.12.3) <20010L3321>. 

The same reaction, the conversion of 2-iodophenol to 2-arylbenzofuranes was also accomplished in the presence of a copper-phenantroline catalyst and caesium carbonate. Different arylacetylenes and iodophenols were coupled to give the corresponding benzofurane derivatives in good to excellent yield (3.55.)71... 

The 7V-arylation of indoles has been achieved both in palladium and copper catalyzed coupling reactions. In an early example Hartwig succeeded in converting indole to 1-arylindoles in excellent yield, using a palladium -dppf catalyst and caesium carbonate as base (6.71.)."a Buchwald99b and... 

The coupling of secondary phosphines with aryl iodides was also extended to pyridines. 3-Iodopyridine and diphenylphosphine were coupled to give 3-diphenylphosphino-pyridine in 60% yield (7.80.), The catalyst in this reaction consisted of copper(I) iodide and N,N -dimethylethylenediamine and caesium carbonate was used again as base.102... 

R. Bunsen, H. Erdmann, and others 15 have made rubidium hydrosulphate, RbHS04. It is obtained by heating the rubidium salt of a volatile acid with sulphuric acid to about 250°-257° the oily liquid, on cooling, forms a crystalline mass of this salt. R. Bunsen made caesium hydrosulphate, CsHS04, by treating caesium carbonate with sulphuric acid under similar conditions. Both salts crystallize from water in rhombic, crystals. 

T. Scheerer found that when heated to a yellow heat (c.1000°), in a closed platinum crucible, potassium carbonate loses about 0 5 per cent, in weight owing to the loss of carbon dioxide which is taken up again at lower temp. W. Dittmar could detect no change when heated to redness in an atm. of carbon dioxide, but it is partially converted into oxide in an atm. of nitrogen, and still more so in an atm. of hydrogen. P. Lebeau found that rubidium and caesium carbonates lose carbon dioxide when heated in vacuo, and, if the vacuum be maintained, decomposition is complete. P. Lebeau also found that the dissociation press, of rubidium carbonate is ... 

Caesium Metavanadate, CsV03, has been obtained by boiling vanadium pentoxide with caesium carbonate solution.6... 

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... 

The chemistry of crown thioethers and thioether cages is a fast-developing field [23], and their synthesis involves a caesium carbonate ring closure [24,25],... 

Based on published procedures for preparing both di- and tri-N-protected tert-butoxycarbonyl (Boc) cyclam derivatives [27], we developed the alternate procedure shown in Scheme 2 for obtaining the tri-branched species 11 [28] as well as related procedures for the new tri-branched derivative 12 (see Scheme 3) [28], the linearly linked derivative 13 [28] and the linked cyclic derivative 14 [29], In the case of the phloroglucinol derivative, tri-Boc protected cyclam was first acylated with chloroacetyl chloride the resulting chloromethylamide was then used to trialkylate phloroglucinol in DMF at 70 °C over caesium carbonate as outlined in Scheme 3. Subsequent... 

It should be noted that while enyne metathesis is considered incompatible with molybdenum catalyst 1, ruthenium catalysts other than the Grubbs type also promote the reaction. Semeril et al. [103] reported efficient enyne RCM with a catalyst conveniently generated in situ from [RuCl2(p-cymene)]2,1,3-bis(mesityl)imidazolium chloride and caesium carbonate. Interestingly the authors found that the in situ derived system gave better results than the isolated catalyst. One of the most impressive examples of the use of enyne RCM is the total synthesis of (-)-longithorone by Layton et al. [104]. Inspired by a pro-... 

For an example of a related cyclisation reaction using caesium carbonate as a base in DMF, see Protocol 3. The starting ditoluenesulfonamide (m.p. 119-20°C) is readily prepared by reaction of the corresponding diamine with p-toluenesulfonyl chloride (aq NaOH/Et2OI. 

Add caesium carbonate (8.26 g, 25.4 mmol) to a solution of 1,5-bis(p-tolu-enesulfonato)-3-oxapentane (5.0 g, 12.1 mmol) in dry DMF (50 mL) in a two-necked round-bottomed flask (250 mL) fitted with an air condenser attached to a nitrogen line. 

Pour into the flask 80 mL of dry dimethylformamide under a slow stream of nitrogen, add a Teflon stirring bar and add caesium carbonate (6.67 g, 0.02 mol). 

This reaction is representative of the synthesis of cyclic thioethers from acyclic dithiols mediated by caesium carbonate in DMF. 

Prepare an oven-dried (electric oven, 105°C, 1 h) double-necked round-bottomed flask (1 L) equipped with a magnetic stirrer bar, fitted with a nitrogen inlet and the pressure-equalised dropping funnel prepared in step 3. Charge the flask with caesium carbonate (13 g, 40 mmol) and dry DMF (350 mL) and heat the stirred suspension to 55°C. 

The versatility of the caesium carbonate-mediated cyclisation reactions in DMF is limited only by the availability and social unacceptability of the... 

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. 

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