Amino acetal catalyst

SCHEME 5.16 The amino acetal catalyst derived from (lS,2S)-5-amino-2,2-dimethyl-4-phenyl-l,3-dioxane (23). 

Reduction of aromatic nitro groups using triethylammonium formate, catalyzed by pal-ladium-on-carbon or a soluble triaryphosphine-palladium acetate catalyst is compatible with ester or amide functions, leading to a-amino esters . The nitro group of the pyra-none 2 is selectively reduced, without hydrogenolysis of the benzyl ether linkage in the presence of finely divided Ni ° ... 

A syn- and enantio-selective Henry reaction employs copper(II) acetate and a chiral -amino alcohol catalyst. 

Early studies desalbe the transesterilication between an active ester and a nucleophile like water catalyzed by amino alcohols [37-46]. For the hydrolysis of active p-nitrophenyl acetates, amino alcohol catalysts served as models for the catalytic diad of serine proteases. Kinetic studies show that the hydrolysis catalyzed by an amino alcohol proceeds via an acylation-deacylation mechanism. 

Hydrolysis of the azlactone leads to the acylaminooinnamic acid the latter may be be reduced catal3rtlcally (Adams PtOj catalyst 40 lb. p.s.i.) and then hydrolysed by hydrochloric acid to the amino acid. Alternatively, the azlactone (say, of a-benzylaminocinnamic acid) may undergo reduction and cleavage with phosphorus, hydriodic acid and acetic anhydride directly to the a-amino acid (d/ p phenylalanine). 

The 4-hydroxy-1-alkene (homoallylic alcohol) 81 is oxidized to the hetni-acetal 82 of the aldehyde by the participation of the OH group when there is a substituent at C3. In the absence of the substituent, a ketone is obtained. The hemiacetal is converted into butyrolactone 83[117], When Pd nitro complex is used as a catalyst in /-BuOH under oxygen, acetals are obtained from homoallylic alcohols even in the absence of a substituent at C-3[l 18], /-Allylamine is oxidized to the acetal 84 of the aldehyde selectively by participation of the amino group[l 19],... 

Ammonium acetate and sodium methoxide are effective catalysts for the ammonolysis of soybean oil (49). Polyfunctional amines and amino alcohols such as ethylenediamine, ethanolamine, and diethanolamine react to give useful intermediates. Ethylenediamine can form either a monoamide or a diamide depending on the mole ratio of reactants. With an equimolar ratio of reactants and a temperature of >250° C, a cyclization reaction occurs to give imidazolines with ethylenediamine (48) ... 

Scheeren et al. reported the first enantioselective metal-catalyzed 1,3-dipolar cycloaddition reaction of nitrones with alkenes in 1994 [26]. Their approach involved C,N-diphenylnitrone la and ketene acetals 2, in the presence of the amino acid-derived oxazaborolidinones 3 as the catalyst (Scheme 6.8). This type of boron catalyst has been used successfully for asymmetric Diels-Alder reactions [27, 28]. In this reaction the nitrone is activated, according to the inverse electron-demand, for a 1,3-dipolar cycloaddition with the electron-rich alkene. The reaction is thus controlled by the LUMO inone-HOMOaikene interaction. They found that coordination of the nitrone to the boron Lewis acid strongly accelerated the 1,3-dipolar cycloaddition reaction with ketene acetals. The reactions of la with 2a,b, catalyzed by 20 mol% of oxazaborolidinones such as 3a,b were carried out at -78 °C. In some reactions fair enantioselectivities were induced by the catalysts, thus, 4a was obtained with an optical purity of 74% ee, however, in a low yield. The reaction involving 2b gave the C-3, C-4-cis isomer 4b as the only diastereomer of the product with 62% ee. 

By selection of conditions and catalyst, the intermediate hydroxyimine (11) can be directed to either (he hydroxy ketone (10) or amino alcohol (12), Over platinum oxide in methanol-acetic acid-water the amino alcohol forms, whereas over alkali-free Ra-Ni in methanol-water or over 10% Pd-on-C in methanol-water containing boric acid, the hydroxy ketones form in excellent yield. Nitrile oxide cycloadditions have been applied to five-membered ring syntheses (.50). 

A mixture of 2.0 g (0.064 mol) of 2-fluoromethyl-3-(o-tolyl)-6-nitro-4(3H)-qulnazolinone, Oi g of 5% palladium-carbon and 100 ml of acetic acid is shaken for 30 minutes in hydrogen gas. The initial pressure of hydrogen gas is adjusted to 46 lb and the mixture is heated with an infrared lamp during the reaction. After 30 minutes of this reaction, the pressure of hydrogen gas decreases to 6 lb. After the mixture is cooled, the mixture is filtered to remove the catalyst. The filtrate is evaporated to remove acetic acid, and the residue is dissolved in chloroform. The chloroform solution is washed with 5% aqueous sodium hydroxide and water, successively. Then, the solution is dried and evaporated to remove solvent. The oily residue thus obtained is dissolved in 2 ml of chloroform, and the chloroform solution is passed through a column of 200 g of silica gel. The silica gel column is eluted with ethyl acetate-benzene (1 1). Then, the eluate is evaporated to remove solvent. The crude crystal obtained is washed with isopropylether and recrystallized from isopropanol. 0.95 g of 2-fluoromethyl-3-(o-tolyl)-6-amino-4(3H)-quinazolinone Is obtained. Yield 52.5% MP 195°-196°C. 

Preparation of 7-amino-3-chloro-3-cephem-4-carboxylic acid To a solution of 750 mg (1 55 mmol) of p-nitrobenzyl 7-amino-3-chloro-3-cephem-4-carboxylate hydrochloride in 20 ml of tetrahydrofuran and 40 ml of methanol was added a suspension of 750 mg of prereduced 5% palladium on carbon catalyst in 20 ml of ethanol and the suspension was hydrogenated under 50 psi of hydrogen at room temperature for 45 minutes. The catalyst was filtered and washed with THF and water. The filtrate and catalyst washes were combined and evaporated to dryness. The residue was dissolved in a water-ethyl acetate mixture and the pH adjusted to pH 3. The insoluble product was filtered and triturated with acetone. The product was then dried to yield 115 mg of 7-amlno-3-chloro-3-cephem-4-carboxylic acid. 

Filtration of the catalyst over a Hyflo pad and removal of the solvent left a yellow crystalline residue. The crude mixture of ketone and potassium acetate was partitioned between methylene chloride (300 cc) and water (1 liter), The layers were separated and the water layer washed with methylene chloride (3 x 50 cc). The organic layers were combined, washed with 3N sodium hydroxide solution (2 x 50 cc), water (3 x 100 cc), dried over anhydrous sodium sulfate and filtered. The solvent was removed and the product recrystallized from ethanol to give 2-amino-2 -fluorobenzophenone as yellow prisms melting at 126° to 128°C,... 

In another study a hyperthermophilic esterase from Aeropyrum pemix K1 (APE1547) was used as a catalyst in the hydrolytic kinetic resolution of rac-3-octanol acetate [53]. Following a single round of epPCR, a mutant displaying a 2.6-fold increase in enantioselectivity was identified having five amino acid substitutions, which were shown to be spatially distal to the catalytic center. 

Pol5uireas were among the first polycondensation pol-5mers to be employed as catal dic supports for heterogeneous metal catalysts. The first report about palladium on polyurea, by Zhang and Neckers [99] dates back to 1979. They obtained their catalyst in a two step preparation, where the co-monomers (2,4- toluendiisocyanate, TDI, and the complex between palladium acetate and 4,4 -di-amino-2,2 -bip5Tiridine) were condensed together and... 

Benzene and naphthalene compounds can be formylated under Vil-smeir conditions. The formyl compounds, with or without isolating, can be condensed with amino arenes to give leuco compounds. In this reaction, the benzhydrol intermediate is not isolated.21,79,84 86 The reaction is generally carried out in an alcohol solvent such as isopropanol, butanol, or pentanol and an acid catalyst such as hydrochloric acid, sulfuric acid, or methanesul-fonic acid.87 Acetic acid can also be used both as catalyst and as the solvent. Urea sometimes is added as catalyst.84,88 Terephthaldehyde reacts with W-diethyl-3-methylaniline89 and substituted azulenes to give a bis-triphenylmethane21 57 and 58, respectively. 

Now, this tentative description of the development of a correlation, later to become information from bases to the synthesis of proteins, by no means solves the problem of the origin of this code nor does it bring into focus the fact that the very proteins which were produced are responsible for the synthesis of the basic metabolic units, formaldehyde and acetic acid and then the amino acids and bases and finally the polymers by catalysts which are the polymers themselves. We do state, however, that the set of reactions quite probably give the most kinetically stable products. Now, the amounts of the different amino acids, lipids, saccharides... 

It was first observed that reactions of imines with ketene silyl acetals proceeded smoothly in the presence of 5mol.% Yb(OTf)3 to afford the corresponding /3-amino ester derivatives in moderate yields.50 However, Sc(OTf)3 was found to be a more active catalyst in this reaction. Benzoylhy-drazones also react with ketene silyl acetals in the presence of a catalytic amount of Sc(OTf)3 to afford the corresponding adducts in high yields (Scheme 11).51 In contrast, catalytic activation of benzoylhydrazones by use of a typical Lewis acid such as TiCl4, SnCl4, or BF3-OEt2, etc. is not effective. 

A more complex reaction is involved in the cooligomerization of acetylenes and tert-butyl isocyanide using nickel acetate as the catalyst (Scheme 20)43 the nature of intermediate complexes leading to the formation of 2-cyano-5-terf-butylaminopyrroles has not been established. Cocyclization of tert-butyl isocyanide with coordinated hexafluoro-2-butyne gives rise to coordinated cyclopentadienone anils for molybdenum systems,44 hence the nature of acetylene substitutents and of the organometallic catalyst play crucial roles in these processes. The pyrrole products from the former reaction can be decomposed by sulfuric acid and the overall sequence provides a simple synthesis of 5-amino-2-cyanopyrroles (Scheme 20). 

---