Ammonium acetate cyclic

A typical manganese-salen complex (27)[89] is capable of catalysing the asymmetric epoxidation of (Z)-alkenes (Scheme 18) using sodium hypochlorite (NaOCl) as the principle oxidant. Cyclic alkenes and a, (3-unsaturated esters are also excellent starting materials for example indene may be transformed into the corresponding epoxide (28) with good enantiomeric excess1901. The epoxidation of such alkenes can be improved by the addition of ammonium acetate to the catalyst system 911. 

Indole derivatives such as dihydroindolone are scaffolds of potentially biological interest. Thus, the development of such functionalized skeletons has been approached by a MCR involving cyclic 1,3-diketones, cyclohexyl isocyanide, aromatic aldehydes, and ammonium acetate in the presence of catalytic amount of KHSO4 in refluxing acetonitrile (Scheme 30) [117]. hi this strategy, the imine derived from the Knoevenagel adduct reacts with cyclohexyl isocyanide to give the... 

V,Af-Dimethylaniline A A,A, AT-Tetramethyl-p-phenylenediamine Cyclic amines 4,4 -Bipyridyl Quinoline Pyridine A-oxide Pyridinium chloride Hydroxides CsOH LiOH NaOH Triton B6 Alkylamines Ammonia Methylamine Ethylamine Propylamine Butylamine Decylamine Dodecylamine Tridecylamine Tetradecylamine Pentadecylamine Hexadecylamine Heptadecylamine Octadecylamine Tributylamine Miscellaneous Ammonium acetate Hydrazine Potassium formate Guanidine... 

Aromatic aldehydes react very easily with tetramic acid under acidic conditions to give 3-benzylidene compounds (41). The yields are moderate, because often there are subsequent reactions. As a,/3-unsaturated carbonyl compounds, (41) react in a Michael addition with excess tetramic acid to form (67), but it can also react with other acyclic and cyclic 1,3-dicarbonyl compounds. In these reactions the aryl substituents may vary over a wide range. Thus, (67) and (68) can be cyclized with ammonium acetate to afford pharmacologically interesting compounds (70) and (71) (90TH1). The latter are dihydropyridines. Curiously, (69) does not cyclize under these conditions. (See Fig. 32.)... 

Fig. 10.3. General electrochemical performance of MPA-Gly-Gly-His modified electrodes for the detection of Cu2+ ions. Cu2+ ions are complexed to Gly-Gly-His in the accumulation process and are electrochemically reduced to Cu(0) to give UPD Cu. (a) Cyclic voltammograms of MPA-Gly-Gly-His modified electrodes in 50 mM ammonium acetate (pH 7.0) and 50 mM NaCl at 25°C at a scan rate of lOOrnVs-1 (i) before accumulation of metal ions and (ii) after accumulation in 46 nM Cu2+ in 50 mM ammonium acetate (pH 7.0) for 10 min. Multiple cycles in the copper voltammogram illustrate stable electrochemistry, (b) Cathodic Osteryoung square wave voltammograms of MPA-Gly-Gly-His modified gold electrodes in 50 mM ammonium acetate (pH 7.0) and 50 mM NaCl (i) before accumulation of metal ions and (ii) after accumulation in 46 nM Cu2+ in 50 mM ammonium acetate (pH 7.0) for 10 min. Reprinted from Ref. [12]. Copyright (2005) with permission from Elsevier.

Fig. 21 Cyclic voltammetry of 31a in acetonitrile as a function of pH. Left under neutral conditions. Right at pH 5.6 (ammonium acetate-acetic acid).

Preparative Methods (i) preparation of racemic DPEN and its optical resolution Reaction of benzil and cyclohexanone in the presence of ammonium acetate and acetic acid at reflux temperature gives a cyclic bis-imine (1) (eq 1). Stereoselective reduction of the bis-imine with lithium in THF-liquid ammonia at —78 °C followed by addition of ethanol, then hydrolysis with hydrochloric acid and neutralization with sodium hydroxide produces the racemic diamine (2). Recrystallization of the l-tartaric acid salt from a 1 1 water-ethanol mixture followed by neutralization with sodium hydroxide, recrystallization from hexane results in (5,5)-DPEN (3) as colorless crystals. 

F.H. Kohnke and co-workers prepared novel heterocyclophanes from cyclic poly-1,4-diketones, which were obtained by the oxidation of calix[6]furan and calix[4]furan. " One of the heterocyclophanes, calix[6]pyrrole, was prepared by the Paal-Knorr pyrrole synthesis from the corresponding dodecaketone. The substrate was heated with excess ammonium acetate in absolute ethanol. Interestingly, the analogous synthesis of calix[4]pyrrole under identical conditions failed, while calix[5]pyrrole is obtained only in 1% yield. 

Either antipode of bromoborane 332 can be prepared in a six-step sequence from benzil (330, Scheme 11-19) [127, 254, 258J. Reaction of benzil with cyclohexanone in the presence of ammonium acetate and acetic acid generates a cyclic bis-imine which is subsequently reduced with lithium in ammonia. The resulting racemic fra .s-imidazolidine is subsequently hydrolyzed to the diamine 331. Resolution of 331 is accomplished by crystallization with either antipode of tartaric acid. The enantiomerically enriched stein ligand 331 is then sulfonylated and condensed with boron tribromide, giving the chiral bromoborane 332. Transmetalla-tion of allyltri-n-butylstannane with bromoborane (R,/ )-332 then affords the allyl-boron reagent (R,/ )-198. 

Figure 8-15. P. aeruginosa azurin on variable-length alkanethiol-modified Au(lll)-electrodes. Cyclic voltammograms, 20 mM ammonium acetate, pH 4.6. The number of methylene groups (n) from A to G are 4, 7, 9, 11, 13, 15, and 17. From ref 49 with permission.

Several recent patents42 127 128 describe the preparation of 4,5-disubsti-tuted oxazole-2-yl alkanoic acids (58) by the reaction of an a-ketol ester with urea in acetic acid or by acetylation of an a-ketol with a cyclic anhydride followed by refluxing with ammonium acetate in acetic acid. 

As alternatives to the chloro compounds for substrates in nucleophilic displacement reactions, phenoxy compounds and cyclic amides and cyclic thioamides have been used. It appears that 2-phenoxyquinoxaline is significantly less reactive than the corresponding cinnoline or phthalazine derivatives and only gives a negligible yield of 2-aminoquinoxaline when heated with ammonium acetate. However the phenoxyquinoxaline 1 is converted in high yield into the aminoquinoxaline 2 on treatment with this reagent. ... 

A SB-P-CD-assisted EKC method for the determination of cyclic nitramine explosives and related degradation intermediates and the 14 ERA listed explosives (borate/SDS electrolyte) has been described. " A volatile electrolyte composed of SB- -CD modified ammonium acetate buffer was selected for the EKC-MS detection of nitroaromatic and cyclic nitramine compounds in soil and marine sediment, as detailed in Table 31.7. The use of phosphate/SDS electrolytes was reported in the separation of the 14 listed nitramine and nitroaromatic explosives for the analysis of extracts of high explosives such as C-4, tetrytol, and detonating cord. " ... 

The GTP, performed in the presence of trimethylsilyldimethylketene acetal as initiator in conjunction with tetrabutyl ammonium acetate catalyst, showed the formahon of cyclic oligomers in addihon to the expected linear oligomers. In contrast, PMMA prepared by radical polymerizahon does not have this functional heterogeneity. MALDl-TOF spectra of low molar mass PMMA, obtained by the polymerizahon of MMA using zir-conocene as initiator, reveal that the process is not a living polymerizahon and that a back-biting cyclizahon process is involved. ... 

Amides can be easily prepared under mild conditions from acid chlorides with ammonium acetate and from oximes by a mild modification of the Beckmann rearrangement Lactams can be prepared by this method from cyclic oximes. and 7-Lactams have been synthesized in a simple manner from aminomalonates a-Aminoacids can be converted into a-ketoacids and related compounds through 2-trifluoromethyl-5-oxazolones... 

Mehta et al. (26) separated guanine on PEI-cellulose with triethylammonium bicarbonate (TEAB) 0.5 M pH 7.6. Good separation of cyclics, phosphates and nucleosides was evident. Trifilo and Dobson (27) separated cyclic purines by PEI, ammonium acetate/hydroxide-ethanol at pH 9.0. One dimension, ascending, from triphosphates to nucleobases. Gulyassy and Farrand (28) also separated cyclic purines with PEI in 0.4 M acetic, then 0.125 M LiCl. Manhandhar and Dyke (29) separated GTP with PEI and luciferase, water and then 1.4 M LiCl for 50 min. Assay was by scintillation counter. 

An additional challenge of biomedical applications of TLC relate to the separations of cyclic nucleotides from noncyclic phosphates. Potter and Yamazaki (48) employed alumina TLC and ammonium acetate pH with ammonium hydroxide to effect these separations. Hynie (49) separated 3 S cGMP using borate impregnated silica in butanol-methanol-ethyl acetate-ammonium hydroxide. Tomasz (SO) separated cyclic pyr/purines on cation exchange, pretreated with HCI, as opposed to the popular anion (PEI) systems. The run with 0.05 M oxalic acid is appealing. 

A dried 10 mL round-bottomed flask was charged with aromatic aldehyde (1 1.0 mmol), cyclic 1,3-diketone (2 1,3-cyclohexanedione or 5,5-dimethyl-l,3-cyclohexanedione 1.0 mmol), p-keto compound (3 2,4-pentadione or acetoacetate derivatives 1.0 mmol), ammonium acetate (4 1.0 mmol), and ceric ammonium nitrate (CAN) (0.05 mmol 5 mol%) followed by 0.5 mL of ethanol. The mixture was then stirred at room temperature until the reaction was completed as monitored by TLC (25 min to 7 h). The resulting reaction mixture was treated with brine solution followed by extraction with ethyl acetate (2 x 20 mL). After evaporation of the solvent, the crude yellow product was recrystalhzed from ethanol to give a yellow or brown solid in good to excellent yield (64-98%). All the products were characterized from their detailed spectral studies including NMR, NMR, EIMS and HRMS. 

Cyclization and folding prepare a buffer solution containing 100 mM ammonium acetate (CH3COONH4) and 20 mM DTT. The peptide concentration should be 1 mg/mL. Stir the solution and monitor the reaction by mass spectrometry. When all the starting material is consumed, purify the cyclic-reduced peptide by RP-HPLC. Folding of the cyclized peptide is carried out in the buffer solutions given in Table 1 for each peptide. 

Yan et al. (2007) reported that polysubstituted annulated pyridines can be synthesized in high yields by four-component, one-pot cyclocondensation reactions of N-phenacyl pyridinium bromide, aromatic aldehydes, acetophenones or cyclic ketones in the presence of ammonium acetate and acetic acid, assisted by microwave irradiation. Cyclic ketones with two a-CH groups yield annulated pyridines with additional a-benzylidene groups, which are derived in situ from double aldol condensation of cyclic ketones with two moles of aromatic aldehydes. 

The reduction of y-nitroketone acetals as in Eq. 6.50 v/ith ammonium formate in the presence of Pd/C gives the correspondmg amines in good yields. However, the reduction ofy-nitro ketones are reduced to cyclic nitrones fEq. 6.51. This reduction is far superior to the classical method using Zn/T4HlCl due to improved yield and simple workup. 

Nitration of the potassium enolates of cycloalkanones with pentyl nitrate81 or nitration of silyl enol ethers with nitronium tetrafluoroborate82 provides a method for the preparation of cyclic a-nitro ketones. Trifluoroacetyl nitrate generated from trifluoroacetic anhydride and ammonium nitrate is a mild and effective nitrating reagent for enol acetates (Eq. 2.41).83... 

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