Bicarbonate as base

The reaction of allylic alcohols and aryl halides in the presence of a palladium catalyst has been used in the past to prepare various 0-arylal-dehydes. The procedure described here is essentially that of Heck and Melpolder.3 A similar reaction has been carried out with bromobenzene and 2-methyl-2-propen-l-ol in hexamethylphosphoric triamide (HMPT) as solvent with sodium bicarbonate as base. A variety of other bases have also been used.4 2-Methyl-3-phenylpropanal has been prepared by reacting palladium acetate and phenylmercuric acetate with 2-methyl-2-propen-l-ol.5... 

Various synthetic protocols were available for the preparation of 1,2,4-triazoles and derivatives thereof Efhcient synthesis of 3,4,5-tri-substituted 1,2,4-triazoles 171 was accompHshed from the reaction of guanidines 169 with 2,2,2-tri-chloroethylimidates 170 in PEG-400 (14TL177). 3,5-Diaryl-l,2,4-triazoles 173 were synthesized from a domino nucleophilic substitution/ oxidative cycfr-zation sequence from 2 equivalents of amidines 172 with copper catalyst, sodium bicarbonate as base, 1,10-phenanthroline as an additive, and K3[Fe(CN)6]/air as the oxidant (14T1635). Sulfur-substituted 1,2,4-triazoles... 

Catalytic asymmetric Staudinger cycloaddition using benzoylquinine as nucleophilic catalyst and sodium bicarbonate as base ... 

Snider and Kwon use either cupric triflate and cuprous oxide or ceric ammonium nitrate and sodium bicarbonate as single-electron oxidants to convert d,s- and ,C-unsaturated enol silyl ethers 9 stereoselectively to the tricyclic ketones 14 in excellent yields [83, 84]. Based on comparison with other experimental data and literature results, the authors try to distinguish between several possible intermediates and propose the following mechanism with a very electrophilic radical cation 10 as the key intermediate. 

The incremental acidification of LRL over a 6-year period resulted in a gradual change in the lake s major ion chemistry such that the composition at pH 4.7 was substantially different from the pH 6.1 conditions. Sulfate increased by a factor of 2.8 and replaced bicarbonate as the major anion. Base cations increased in the water column at each treatment pH such that at pH 4.7 total base-cation concentration increased 56% over preacidification values. Increases in Ca2+ accounted for about 75% of the increase in total base-cation concentration. 

The allylic alcohol substitution reaction may also be carried out in DMF solution with sodium bicarbonate as the base at 100 to 125° with palladium-phosphine catalysts, in which case only carbonyl products are formed. With this catalyst combination nonallylic, unsaturated alcohols also react to form carbonyl compounds in good yields. For example, in an extreme case, 9-decen-l-ol and bromobenzene gave some 10-phenyldecanal (40) ... 

Allylic alcohols also may be arylated in / /-methylpyrrolidinone or DMF solution with sodium bicarbonate as the base.81 The use of this base improves the yields of aldehydes obtained compared with tertiary amine bases in the case of aryl bromides with electron-withdrawing substituents, where reduction to an arene is sometimes a problem,... 

R-(R, S )]-p-Methyl-a-phenyl-1-pyrrolidineethanol is an important chiral mediator for the enantioselective addition of an acetylide to a prochiral ketone.2 3 This reaction has been successfully applied to the synthesis of the reverse transcriptase inhibitor efavirenz (DMP-266) (Scheme 1).3.4 Preparation of the enantiomer, (1S,2R)-N-pyrrolidinylnorephedrine, has been reported.2 The method used potassium carbonate (K2CO3) as base, but the yield of the product was only 33%. The submitters have extensively studied the formation of the pyrrolidinyl ring under various conditions as summarized in Table I. Eventually they found that the reaction was extremely efficient when it was run in toluene using sodium bicarbonate (NaHCC>3) as base (entry 8, Table I),5 which gave [R-(R, S )]-p-methyl-a-phenyl-1-pyrrolidineethanol quantitatively. Enantioselective (up to 99% ee) addition of cyclopropylacetylene to the ketoaniline 1 is achieved when the solution of [R-(R, S )]-p-methyl-a-phenyl-1-pyrrolidineethanol is used as a chiral additive.3 In addition, this method is also applicable to the preparation of a variety of alkylated norephedrines and other amino alcohols in excellent yields as Illustrated in Table II. These amino alcohols are potentially useful in asymmetric syntheses. 

The hypothesis that intravenous fluid that contains sodium bicarbonate might decrease the incidence of CIN compared with NaCl was recently tested in some randomized trials [113-116]. The hypothesis for a potential benefit of bicarbonate is based on the concept that alkalinizing tubular fluid reduces the generation of injurious hydroxyl radicals. Within a retrospective Cohort Study of 7977 Patients at Mayo Clinic N-ace-tylcysteine alone and in combination with sodium bicarbonate was not associated with any significant difference in the incidence of contrast nephropathy. The use of intravenous sodium bicarbonate was associated with increased incidence of contrast nephropathy [117]. As with any retrospective study confounding by indication is always exists since patients at preceived high risk often receive the treatment that is suspected of being superior even when unproven. 

Because of the ubiquitousness of carbonate rocks and the equilibrium reactions of CO2, bicarbonate and carbonate are present as bases in most natural waters. In addition, small concentrations of the bases borate, phosphate, arsenate, ammonia, and silicate may be present in the solution. Volcanoes and certain hot springs may yield strongly acid water by adding gases like HCl and SO2. 

If ingestion has occurred, emesis or gastric lavage may be useful if initiated within 30 min. If acidosis is present, it can be treated with intravenous sodium bicarbonate as needed. Hemodialysis may be indicated in cases of severe acid-base and/or fluid-electrolyte abnormalities or in cases of renal failure. Animal data suggest that ethanol therapy may inhibit the formation of toxic metabolites. 

Bromoethyl)indole, on treatment with potassium carbonate in refluxing acetonitrile, gives a stable spirocyclopropyl-indolenine, however this cyclisation is very slow when sodium bicarbonate is used as base and this allows efficient Af-alkylation of piperidines with the bromide. Nucleophiles, such as organo-lithiums and enolates, add to the indolenine without disrupting the cyclopropane ring. °... 

If any two of the variables are known, the third can always be calculated. Indeed, blood gas analyzers (Fig. I) are programmed to provide this information which is printed out on the report I orni and usually includes the measured POi us well. There are a multitude of other calculated values oit some blood gas analyzer print outs, such as base excess and standard bicarbonate. These nitty be mostly disregarded in the routine assessment of a patient s acid-base balance. 

Whiting used Mc2NH for the Mannich reaction and found that the elimination step could be carried out with bicarbonate as the very mild base. The hydroxylation was done by epoxidation and hydrolysis. 

Heck and related reactions. In < While Et N is used as base in many He< acetate or bicarbonate together with a i tion of alkenes is subject to a remarkaM... 

Caustic soda is the base most commonly used, but the alkali carbonates and bicarbonates as well as the alkaline-earth hydroxides all find occasional application. Potassium compounds show no advantage over the cheaper so um materials, except that potassium hydroxide in some alkaline fusions permits the use of a lower temperature. Ammonium hydroxide and ammonium salts are rardy used. Chloroform has occasionally bear used as a solvent. 

Bicarbonate ion (the conjugate base of carbonic acid) is a strong enough base to deprotonate benzoic acid but not p-methylphenol. A typical scheme for the separation of these compounds from a mixture using bicarbonate as the base is shown on the next page. 

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