Sonicated reaction

Unlike amidines, the multicomponent reaction of a,(3-unsaturated ketones 96 (aliphatic [94] or aromatic [95, 96]) with carbonyl compounds 97 and ammonia, which are the synthetic precursors of amidines, yielded 1,2,5,6-tetrahydropyrimidines 98 instead of dihydroheterocycles. When R3 is not the same as R4 tetrahydropyrimidines 98 were mixtures of diastereomers A and B, in which the relative configurations of stereogenic centers were also established [95, 96]. In contrast to conventional mechanical shaking requiring about 48 h [95], sonicated reactions were completed within 90 min at room temperature and provided the target heterocycles in high yields and purities [96]. Ultrasonic irradiation also significantly expanded the possibilities of such three-component reactions (Scheme 3.29). 

The appearance of a Symposium-in-Print on aspects of carbene chemistry is obviously relevant to those interested in cyclopropane chemistry. Sonication reactions are becoming increasingly popular... 

The acid-catalyzed hydrolysis of ethyl acetate was studied at three frequencies, 400, 700, and 1500 kHz, and various energy levels. Differences in rate between the sonicated and non-sonicated reactions fall for most of them within the experimental error. In a weakly basic medium, the rate increase of the sonicated hydrolysis of 4-nitrophenyl esters is a modest 15%. On the other hand, the... 

The substitution of chlorine by azide (Eq. 24) in 4-pyridyl-chlorodiazirine was studied using isotopically labelled ions.l33 The SrnI mechanism was established from the label content of the final nitrile.i34 In the dark in DMSO solution, the sonicated reaction proceeds much faster than in the absence of ultrasound. The sensitivity to sonication was used to propose the SET mechanism, confirmed in further works. 

The reactions of the same azadiene with quinones were examined in a second set of experiments, and the sonochemical effect in terms of rates and yields is larger than with non-quinonic dienophiles. Aromatization of the adduct generally occurs by elimination of dimethylamine and oxidation of the dihydro compound. The sonicated reactions with 1,4-benzo- and naphthoquinones are successful even in an acetonitrile solution. 

In most cases, the sonicated reactions proceed faster than the thermal ones by a factor of ca. 6, in equivalent or slightly better yields. The similarity of the sonochemical results with that of high-pressure reactions was observed in two examples where they were tested. ... 

In an acetonitrile suspension, the intermediate a-cyanoalkoxide can be trapped by acyl chlorides to give cyanohydrin esters. In a preparation of synthetic pyrethroids, the comparison between the sonicated reaction and its PTC equivalent gave an advantage to the latter in terms of reaction time and yield. i A modest change in stereoselectivity is observed in some cases. The same reaction in the presence of ammonium chloride leads to a-amino nitriles, the first step of the Strecker amino acid synthesis.4 72 xhe procedure is more efficient in the presence of alumina. The formation of by-products, cyanohydrins or benzoins, is avoided. From an experimental viewpoint, the work-up is considerably easier than with conventional procedures, and consists mostly of a simple filtration. With ketones, and in the presence of ammonium carbonate, a hydantoin is formed (Eq. 21)7 ... 

The protection of hydroxyl groups as methoxymethyl (MOM) ethers was achieved in a simple and convenient solvent-free reaction on alumina under sonication (Eq. 54).The reactions are generally reasonably fast and high-yielding and conditions are mild enough not to induce isomerization of double or triple bonds in allylic and propargylic alcohols. Alumina can be recycled after washing and reactivation. Without sonication, reactions were very slow. 

The problem of recovering the heterogeneous catalyst after the sonication reaction in a slurry reactor (SR) is an important one on the industrial scale. In fact the breaking of the catalytic particles, due to ultrasound action, can produce a very fine powder recoverable only with difficulty by filtration, and therefore easily contaminating the reaction products. The authors of the present chapter have faced this problem for the phase transfer (PT) alkylation of phenylacetonitrile with butyl bromide (Eq. 11) using a PT catalyst supported on insoluble polystyrene cross-linked with divinylbenzene. ... 

An improvement of the allylation reaction was achieved with the use of ultrasonic waves in a water-tetrahydrofuran (5/1) mixture without the help of acidic co-reagents (Petrier et al., 1985). Noteworthy are the sonicated reactions involving commercially available aqueous solutions of aldehydes, such as formaldehyde, and those involving aldehydes containing free hydroxyl groups (Einhom and Luche, 1987) ... 

In plasma chromatography, molecular ions of the heavy organic material to be analy2ed are produced in an ionizer and pass by means of a shutter electrode into a drift region. The velocity of drift through an inert gas at approximately 101 kPa (1 atm) under the influence of an appHed electric field depends on the molecular weight of the sample. The various sonic species are separated and collected every few milliseconds on an electrode. The technique has been employed for studying upper atmosphere ion molecule reactions and for chemical analysis (100). 

Deflagration A propagating chemical reaction of a substance in which the reaction front advances into the unreacted substance at less than the sonic velocity in the unreacted material. Where a blast wave is produced that has the potential to cause damage, the term explosive deflagration may be used. 

The combination of alkali metal acid fluorides and porous aluminum fluoride IS a stable, solid, and efficient substitute for anhydrous hydrogen fluoride for promoting the ring-opening reactions of simple aliphatic oxiranes to give the fluorohydrins under sonication [/5] (equations 14 and 15)... 

Under sonication conditions, the reaction of perfluoroalkyl bromides or iodides with zinc can be used to effect a variety of functionalization reactions [39, 40, 41, 42] (equation 30) Interestingly, the ultrasound promoted asymmetric induction with the perfluoroalkyl group on the asymmetric carbon was achieved by the reaction of perfluoroalkyl halides with optically active enamines in the presence of zinc powder and a catalytic amount of dichlorobisftc-cyclopenta-dienyl)titanium [42] (equation 31)... 

Chemical reaction equilibrium calculations are structured around another thermodynamic term called tlie free energy. Tliis so-callcd free energy G is a property that also cannot be defined easily without sonic basic grounding in tlicmiodynamics. However, no such attempt is made here, and the interested reader is directed to tlie literature. " Note that free energy has the same units as entlialpy and internal energy and may be on a mole or total mass basis. Some key equations and information is provided below. 

The mitochondrial complex that carries out ATP synthesis is called ATP synthase or sometimes FjFo-ATPase (for the reverse reaction it catalyzes). ATP synthase was observed in early electron micrographs of submitochondrial particles (prepared by sonication of inner membrane preparations) as round, 8.5-nm-diameter projections or particles on the inner membrane (Figure 21.23). In micrographs of native mitochondria, the projections appear on the matrixfacing surface of the inner membrane. Mild agitation removes the particles from isolated membrane preparations, and the isolated spherical particles catalyze ATP hydrolysis, the reverse reaction of the ATP synthase. Stripped of these particles, the membranes can still carry out electron transfer but cannot synthesize ATP. In one of the first reconstitution experiments with membrane proteins, Efraim Racker showed that adding the particles back to stripped membranes restored electron transfer-dependent ATP synthesis. 

Reaction of aniline derivatives with 4-chlorobutyroyl chloride followed by cyclization with sodium ethoxide and subsequent thionation promoted by sonication gave the corresponding A -arylpyrrolidine-2-thiones 126. Zinc-mediated condensation of diethyl bromomalonate with 126 using iodine as activator gave the vinylogous urethanes 127 whose cyclization with PPA gave the tricyclic compound 128 which upon hydrolysis afforded the acid 129 (96TL9403). 

THF). The authors found that the yield could be increased to 95 % by sonication of the reaction vessel, for the reaction in THF. The ionic liquid was then used to extract the manganese by-products and impurities from an ethyl acetate solution of the product [63]. 

The next major obstacle is the successful deprotection of the fully protected palytoxin carboxylic acid. With 42 protected functional groups and eight different protecting devices, this task is by no means trivial. After much experimentation, the following sequence and conditions proved successful in liberating palytoxin carboxylic acid 32 from its progenitor 31 (see Scheme 10) (a) treatment with excess 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) in ie/t-butanol/methylene chloride/phosphate buffer pH 7.0 (1 8 1) under sonication conditions, followed by peracetylation (for convenience of isolation) (b) exposure to perchloric acid in aqueous tetrahydrofuran for eight days (c) reaction with dilute lithium hydroxide in H20-MeOH-THF (1 2 8) (d) treatment with tetra-n-butylammonium fluoride (TBAF) in tetrahydrofuran first, and then in THF-DMF and (e) exposure to dilute acetic acid in water (1 350) at 22 °C. The overall yield for the deprotection sequence (31 —>32) is ca. 35 %. 

J Reagents R M also used CH2 = CHCH2SnBu3/TiCl4(2 equiv), -78°C34 CH, = CHCH2-9-BBN, -78°C34. Reaction performed under sonication. 

Many reactions have been shown to benefit from irradiation with ultrasound (ref. 19). We therefore decided to investigate the effect of ultrasound, different catalysts and the presence of solids on Ullmann diaryl ether synthesis. Indeed, sonication of mixtures of a phenol and a bromoaromatic compound, in the absence of solvent and presence of copper (I) iodide as catalyst and potassium carbonate as base, produces good yields of diaryl ethers at relatively low temperatures (Fig. 10) (ref 20). 

A variation of this transfonnation reacts the acid with hthium naphthalenide in the presence of 1-chlorobutane. The product is the ketone. A related reaction treats the lithium carboxylate with lithium metal and the alkyl halide, with sonication, to give the ketone. ... 

The concept of linear burning rate is not confined to the reaction of a gas with a solid. The fuses on fireworks are designed to bum at a constant linear rate. The flame front on solid rocket fuel progresses at a constant linear rate. Both examples have two reactants (a fuel and an oxidizer) premixed in the soUd. Heat transfer limits the burning rate. These materials are merely fast burning. Unlike explosives, they not do propagate a sonic shockwave that initiates further reaction. 

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