Room Temperature Acid Catalysts

Bj Pivaloyloxymethyl D(—)-Ot-aminobenzylpenicillinate. hydrochloride To a solution of pivaloyloxymethyl D(—)-a-azidobenzylpenicillinate (prepared as described above) in ethyl acetate (75 ml) a 0.2 M phosphate buffer (pH 2.2) (75 ml) and 10% palladium on carbon catalyst (4 g) were added, and the mixture was shaken in a hydrogen atmosphere for 2 hours at room temperature. The catalyst was filtered off, washed with ethyl acetate (25 ml) and phosphate buffer (25 ml), and the phases of the filtrate were separated. The aqueous phase was washed with ether, neutralized (pH 6.5 to 7.0) with aqueoussodium bicarbonate, and extracted with ethyl acetate (2 X 75 ml). To the combined extracts, water (75 ml) was added, and the pH adjusted to 25 with 1 N hydrochloric acid. The aqueous layer was separated, the organic phase extracted with water (25 ml), and the combined extracts were washed with ether, and freeze-dried. The desired compound was obtained as a colorless, amorphous powder. 

Aryldiazoalkanes have therefore been developed because they react readily with carboxylic acids at room temperature without catalysts. These are generally unstable against heating and light and cannot therefore be well purified by recrystallization. 

Inl989, Yamamoto introduced the chiral (acyloxy)borane (CAB) complex for catalytic asymmetric Diels-Alder reactions [18], which has been utilized as a magic hand catalysis for the aldol synthesis and for the Sakurai-Hosomi reaction so far [19,20]. In contrast to R=H of 17, which is both air and moisture sensitive, the B-alkylated catalyst, R=Ph or alkyl, is stable and can be stored in closed containers at room temperature. This catalyst is easily prepared from phenyl- or alkylboric acid and 16 simple mixing of a 1 1 molar ratio of the ester 16 and phe-... 

B. Tetrahydro-Binor-S. Binor-S (135.0 g., 0.73 mole) is dissolved in 670 ml. of glacial acetic acid containing 5.7 ml. of concentrated hydrochloric acid. To this solution is added 1.0 g. of platinum oxide catalyst. The reaction mixture is hydrogenated at 200 p.s.i. hydrogen pressure and 70° for 3 hours using a 1200-ml. glass-lined autoclave (Note 5). fter cooling to room temperature, the catalyst is removed by suction filtration and water is added to the filtrate until two layers form. About... 

A similar methodology was applied by Colonna et al. [101] to the oxidation of aryl alkyl sulfides with Bu OOH as oxidizing agent and a catalytic amount of a titanium A-salicylidene-L-amino acid complex (47) (0.1 mol equiv) in benzene at room temperature. This catalyst is not very enantioselective, and often yields mixtures of sulfoxides and sulfones. The highest enantioselectivity was achieved in the oxidation of f-butyl (p-nitrophenylthio)acetate, which gave sulfoxide in 21% ee and 25% yield. Like the Kagan reagent, but to a lesser measure, the use of a stoichiometric amount of titanium complex substantially influences the enantioselectivity, which increases from 12% (catalytic) to 21% (stoichiometric) for the oxidation of methyl p-tolyl sulfide. 

Silica sulfuric acid efficiently catalyzed the electrophilic substitution reaction of indoles with varions isatins in dichloromethane to afford the corresponding oxindole derivatives in high yields at room temperature. The catalyst exhibited ranarkable reusable activity (Scheme 2.11) (Azizian et al. 2006). 

The first Lewis acid-catalyzed asymmetric Michael addition in water was developed by Kobayashi et al, who reported ee s up to 83%. Very recent developments show great promise for further improvement of Michael addition reactions in water. In an elegant study, Kaneda and coworkers used montmorillonite-enwrapped metal triflates to execute C—C bond forming Michael additions. When scandium triflate was employed, adducts were obtained in quantitative yield within a 0.5-3 h at or slightly above room temperature. The catalysts were reusable with no appreciable loss in activity.In another recent study, Lind-strdm and coworkers observed a remarkable ligand acceleration effect in aqueous ytterbium triflate-catalyzed Michael additions. A number of 1,2-diamines and 1,2-aminoalcohols were shown to have a positive influence on the rate of the reaction, the most efficient being tetramethylethylenediamine, which induced a nearly 20-fold rate acceleration. 

Scandium trifluoromethanesulfonate has been found to be a Lewis acid catalyst for selective cleavage of esters containing a coordinative group adjacent to an ester moiety (Scheme 35). The reaction proceeded under weak acidic conditions at room temperature the catalyst could be recovered and reused. Even a-acyloxy ketones were deacetylated without racemization. A series of lanthanide complexes, Ln N[S020CH(CF3)2]2 3, have been shown to be very effective catalysts for... 

Probably unjustly these have been somewhat neglected as protective groups, except perhaps in the carbohydrate field. They are prepared by acid-catalyzed reaction of carbonyl compounds with alkyl thiols or with dithiols. The conditions which have been used include ethanedithiol in acetic acid-boron trifluoride [73], ethane-thiol or -dithiol in the presence of hydrogen chloride [81, 82, 83], or in dioxan in the presence of zinc chloride [84]. An interesting alternative is offered by the reaction of carbonyl compounds with ortho-thioboric esters at room temperature without catalyst [85]. 

Because V is very electrophilic in VO(OR)3 (J(V) = -1-0.46) [8], this reaction occurs within seconds at room temperature without catalyst. By comparison, exchange of OPr for OEt in Si(OEt)4 (J(Si) = -1-0.32) takes about twenty hours with acid catalyst [116]. ... 

The benzoic acid derivative 457 is formed by the carbonylation of iodoben-zene in aqueous DMF (1 1) without using a phosphine ligand at room temperature and 1 atm[311]. As optimum conditions for the technical synthesis of the anthranilic acid derivative 458, it has been found that A-acetyl protection, which has a chelating effect, is important[312]. Phase-transfer catalysis is combined with the Pd-catalyzed carbonylation of halides[3l3]. Carbonylation of 1,1-dibromoalkenes in the presence of a phase-transfer catalyst gives the gem-inal dicarboxylic acid 459. Use of a polar solvent is important[314]. Interestingly, addition of trimethylsilyl chloride (2 equiv.) increased yield of the lactone 460 remarkabiy[3l5]. Formate esters as a CO source and NaOR are used for the carbonylation of aryl iodides under a nitrogen atmosphere without using CO[316]. Chlorobenzene coordinated by Cr(CO)j is carbonylated with ethyl formate[3l7]. 

The 3-alkyi-1,3-butadiene-2-carboxylate (2-vinylacrylate) 850 is obtained in a high yield by the carbonylation of the 2-alkyl-2,3-butadienyl carbonate 849 under mild conditions (room temperature, atm)[522]. The corresponding acids are obtained in moderate yields by the carbonylation of 2,3-alkadienyl alcohols under severe conditions (100 °C, 20 atm) using a cationic Pd catalyst and p-TsOH[523],... 

With acid catalysts, butyrolactone reacts with alcohols rapidly even at room temperature, giving equiUbtium mixtures consisting of esters of 4-hydroxybutyric acid [591-81-1] with unchanged butyrolactone as the main component. Attempts to distill such mixtures ordinarily result in complete reversal to butyrolactone and alcohol. The esters can be separated by a quick flash distillation at high vacuum (149). 

Hydration and Dehydration. Maleic anhydride is hydrolyzed to maleic acid with water at room temperature (68). Fumaric acid is obtained if the hydrolysis is performed at higher temperatures. Catalysts enhance formation of fumaric acid from maleic anhydride hydrolysis through maleic acid isomerization. 

The tertiary metal phosphates are of the general formula MPO where M is B, Al, Ga, Fe, Mn, etc. The metal—oxygen bonds of these materials have considerable covalent character. The anhydrous salts are continuous three-dimensional networks analogous to the various polymorphic forms of siHca. Of limited commercial interest are the alurninum, boron, and iron phosphates. Boron phosphate [13308-51 -5] BPO, is produced by heating the reaction product of boric acid and phosphoric acid or by a dding H BO to H PO at room temperature, foUowed by crystallization from a solution containing >48% P205- Boron phosphate has limited use as a catalyst support, in ceramics, and in refractories. 

AHyl alcohol can be easily oxidized to yield acrolein [107-02-8] and acryhc acid [79-10-7]. In an aqueous potassium hydroxide solution of RuQ., aHyl alcohol is oxidized by a persulfate such as K2S20g at room temperature, yielding acryhc acid in 45% yield (29). There are also examples of gas-phase oxidation reactions of ahyl alcohol, such as that with Pd—Cu or Pd—Ag as the catalyst at 150—200°C, in which ahyl alcohol is converted by 80% and acrolein and acryhc acid are selectively produced in 83% yield (30). 

Few aHyl monomers have been polymerized to useful, weH-characterized products of high molecular weight by ionic methods, eg, by Lewis acid or base catalysts. Polymerization of the 1-alkenes by Ziegler catalysts is an exception. However, addition of acidic substances, at room temperature or upon heating, often gives viscous liquid low mol wt polymers, frequently along with by-products of uncertain stmcture. 

Succinic anhydride can be prepared from succinic acid by dehydration it operates in high boiling solvent (31), in the presence of clays as a catalyst (32), or at room temperature with triphosgene (33). 

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