In situ preparations

The desired pyridylamine was obtained in 69 % overall yield by monomethylation of 2-(aminomethyl)pyridine following a literature procedure (Scheme 4.14). First amine 4.48 was converted into formamide 4.49, through reaction with the in situ prepared mixed anhydride of acetic acid and formic acid. Reduction of 4.49 with borane dimethyl sulfide complex produced diamine 4.50. This compound could be used successfully in the Mannich reaction with 4.39, affording crude 4.51 in 92 % yield (Scheme 4.15). Analogous to 4.44, 4.51 also coordinates to copper(II) in water, as indicated by a shift of the UV-absorption maximum from 296 nm to 308 nm. 

Two approaches have been taken to produce metal-matrix composites (qv) incorporation of fibers into a matrix by mechanical means and in situ preparation of a two-phase fibrous or lamellar material by controlled solidification or heat treatment. The principles of strengthening for alloys prepared by the former technique are well estabUshed (24), primarily because yielding and even fracture of these materials occurs while the reinforcing phase is elastically deformed. Under these conditions both strength and modulus increase linearly with volume fraction of reinforcement. However, the deformation of in situ, ie, eutectic, eutectoid, peritectic, or peritectoid, composites usually involves some plastic deformation of the reinforcing phase, and this presents many complexities in analysis and prediction of properties. 

The third generation are latices made with independentiy prepared surfactant to mimic the in situ prepared functional monomer surfactant. These emulsifiers are often A—B block polymers where A is compatible with the polymer and B with the aqueous phase. In this way surface adsorption of the surfactant is more likely. These emulsions are known to exhibit excellent properties. 

In situ preparation of polymer blends of 1,4-polybutadiene with polystyrene, or poly(l-butene) has been achieved by using the heterogeneous Ziegler-Natta type catalyst (C2H )2A1C1—Ti(OC4H )4 in the host polymers (217). Homogeneous catalysts can also be used to catalyze these reactions (218). 

In contrast to many other surface analytical techniques, like e. g. scanning electron microscopy, AFM does not require vacuum. Therefore, it can be operated under ambient conditions which enables direct observation of processes at solid-gas and solid-liquid interfaces. The latter can be accomplished by means of a liquid cell which is schematically shown in Fig. 5.6. The cell is formed by the sample at the bottom, a glass cover - holding the cantilever - at the top, and a silicone o-ring seal between. Studies with such a liquid cell can also be performed under potential control which opens up valuable opportunities for electrochemistry [5.11, 5.12]. Moreover, imaging under liquids opens up the possibility to protect sensitive surfaces by in-situ preparation and imaging under an inert fluid [5.13]. 

Deuterioboration is one of the most important recent additions to the array of methods for saturating double bonds with deuterium. The easy accessibility of metal deuterides (lithium aluminum deuteride or sodium borodeuteride) facilitates the in situ preparation of deuteriodiborane which reacts with steroidal double bonds with a high degree of site and/or stereospecificity, depending on the location of the double bond. " ... 

The method of Fried and Sabo for the in situ preparation of hypobromous acid from A-bromoacetamide (or A-bromosuccinimide) in aqueous dioxane or acetone containing perchloric acid is commonly used, e.g., (81) (82). 

Because the vinylzinc and vinylcadmium reagents can be prepared directly from the vinyl halides (I, Br) with zinc or cadmium metal, this route avoids cross coupling processes and provides a one-pot in situ preparation of perfluo-rovinylcopper compounds Table 7 shows examples of this method of preparation of vinylcopper reagents from the indicated cadmium or zinc reagent [145]... 

Nal increases the reactivity of MOMCl by the in situ preparation of MOMI, which facilitates the protection of tertiary alcohols. ... 

ZnBr2, CH2CI2, 25°, 2-10 h, 90% yield. When a MEM-protected diol was cleaved using ZnBt2 EtOAc, 1,3-dioxolane formation occurred, but this can be prevented by the use of in situ-prepared TMSI. ... 

NaH, /7-MeOQH4CH2Br, DMF, —5°, 1 h, 65%. Other bases, such as BuLi, ° dimsyl potassium," and NaOH under phase-transfer conditions," have been used to introduce the MPM group. The use of (n-Bu)4N I for the in situ preparation of the very reactive p-methoxybenzyl iodide often improves the protection of hindered alcohols." In the following example, selectivity is probably achieved because of the increased acidity of the 2 -hydroxyl group ... 

For the in situ preparation of the required arenediazonium salt from an aryl amine by application of the diazotization reaction, an acid HX is used, that corresponds to the halo substituent X to be introduced onto the aromatic ring. Otherwise—e.g. when using HCl/CuBr—a mixture of aryl chloride and aryl bromide will be obtained. The copper-(l) salt 2 (chloride or bromide) is usually prepared by dissolving the appropriate sodium halide in an aqueous solution of copper-(ll) sulfate and then adding sodium hydrogensulfite to reduce copper-(ll) to copper-(1). Copper-(l) cyanide CuCN can be obtained by treatment of copper-(l) chloride with sodium cyanide. 

Usually, in situ preparation in Barbier-type carbonyl additions are carried out with the bromides or chlorides even sterically blocked carboxylates, such as 2,4,6-trimethylbenzoic acid esters, can be used successfully15. The reactions are accelerated by ultrasound16,17. 

Both reagents 7 and 9 are also excellently suited for the introduction of 3-substituted allyl residues. Both high simple anti) diastereoselectivity and enantioselectivity are observed, irrespective of the configuration of the double bond in the allylmagnesium, -potassium, or -lithium reagent used for the in situ preparation 11,35 36. 

The condensation is usually carried out by adding a solution containing equimolar amounts of the allyl halide and the aldehyde or ketone to a solution of at least two equivalents of chromium-(II) chloride in THF at 0 5°C. Frequently, the less precious component is used in 50-100% excess. Although commercially available anhydrous chromium(II) chloride can be utilized (Method B), its in situ preparation from chromium(III) chloride and lithium aluminum hydride (Method A) is often preferred. The removal of chromium and aluminum hydroxide, which are formed on aqueous workup, can be accomplished by filtration in the presence of a filtration aid. 

Combination of nickel bromide (or nickel acetylacetonate) and A. A -dibutylnorephcdrinc catalyzed the enantioselective conjugate addition of dialkylzincs to a./Tunsaturated ketones to afford optically active //-substituted ketones in up to ca. 50% ee53. Use of the nickel(II) bipyridyl-chiral ligand complex in acetonitrile/toluenc as an in situ prepared catalyst system afforded the //-substituted ketones 2, from aryl-substituted enones 1, in up to 90% ee54. 

The most convenient method is the formation of two equivalents of (25) by retro-aldol cleavage from commercially available (26) by the combined action of FruA and triose phosphate isomerase (Figure 10.18 inset) [84]. This scheme has been extended into a highly integrated, artificial metabolism for the efficacious in situ preparation of (25) from inexpensive feedstock such as glucose and fructose (two equivalents of... 

Sodium disulfide for the in situ preparation of organic disulfanes R2S2 may also be prepared from the elements in 1,2-dimethoxyethane at 70 °C in the presence of catalytic amounts of an aromatic hydrocarbon or ketone [22]. 

The enantioselective 1,4-addition addition of organometaUic reagents to a,p-unsaturated carbonyl compounds, the so-called Michael reaction, provides a powerful method for the synthesis of optically active compounds by carbon-carbon bond formation [129]. Therefore, symmetrical and unsymmetrical MiniPHOS phosphines were used for in situ preparation of copper-catalysts, and employed in an optimization study on Cu(I)-catalyzed Michael reactions of di-ethylzinc to a, -unsaturated ketones (Scheme 31) [29,30]. In most cases, complete conversion and good enantioselectivity were obtained and no 1,2-addition product was detected, showing complete regioselectivity. Of interest, the enantioselectivity observed using Cu(I) directly in place of Cu(II) allowed enhanced enantioselectivity, implying that the chiral environment of the Cu(I) complex produced by in situ reduction of Cu(II) may be less selective than the one with preformed Cu(I). 

Finally, an alternative in situ preparation of the silyl iodide 1789 from tetramethyl-disiloxane 1788 has been described. The silyl iodide 1789 reduces aromatic aldehydes, such as benzaldehyde 1790 a, or ketones such as acetophenone, 1790b, into the iodides 1791 a,b, andquinones 1792 into the hydroquinones 1793 [33] (Scheme 12.11). 

Basol BB (1988) Electrodeposited CdTe and HgCdTe solar Cells. Sol Cells 23 69-88 Bhattacharya RN, Rajeshwar K, Noufi RN (1985) In situ preparation of p-Type CdTe thin films by cathodic electrodeposition. J Electrochem Soc 132 732-734 Llabres J (1984) In situ preparation of undoped p-Type CdTe by cathodic electrochemical deposition. J Electrochem Soc 131 464 65... 

Xi D, Pei Q (2007) In situ preparation of free-standing nanoporous alumina template for polybithiophene nanotube arrays with a concourse base. Nanotechnology 18 095602... 

All examples mentioned so far correspond to reactions between two aromatic groups, however, couplings in which one or both partners are alkyl groups can be achieved using electron-rich boron-based nucleophiles. Fiirstner has reported the use of B-alkyl or 5-allyl methoxy-9-BBN anions for the efficient coupling with some aryl chlorides using an in situ prepared IPr HCl/Pd(OAc)j system [118], Some of the results obtained with these easy-to-handle borate-based nucleophiles are shown below (Scheme 6.34). 

Closely related transformations were also catalyzed by the in situ prepared lan-thanum-lithium-BINOL (LLB) catalyst developed by Shibasaki (Scheme 5-28). 

It is important to remember that the yield and reproducibility of hydrozircona-tions and the subsequent transformations depend on the presence of ionic impurities in 1 which often hamper the desired transformations. For example, in situ preparations of 1 with liEtjBH and BuMgCl were not appropriate for hydrozircona-tion/copper-catalyzed conjugate addition sequences otherwise preformed 1 is well adapted for these protocols. 

The efficiency of the new ligands was examined in enantioselective hydrogenation of some prochiral substrates. Itaconic ester hydrogenation using in situ prepared Rh-complexes was the first test reaction chosen. The best results from... 

Chiral and achiral Jacobsen s catalysts exhibit similar diatereomeric excesses during the diastereoselective epoxidation of R-(+)-limonene using in situ prepared oxidizing agents. Therefore, the chiral center of the substrate appears to govern the chiral induction. In contrast, the chirality of the Jacobsen s catalyst appears to be responsible for the chiral induction when commercially available oxidants were used. 

Asymmetric addition to ketimine in a reagent controlled manner has seldom been reported, even by 2008. When we investigated the potential for tbis asymmetric addition around 1992, there were no known examples. In 1990, Tomioka et al., reported the first asymmetric addition of alkyl lithium to N-p-methoxyphenyl aldo-imines in the presence ofa chiral (3-amino ether with 40-64% ee [8] (Scheme 1.11). In 1992, Katritzky reported the asymmetric addition of Et2Zn to in situ prepared N-acyl imine in the presence of a chiral (3-amino alcohol with 21-70% ee [15] (Scheme 1.12). In the same year, Soai et al., reported the asymmetric addition of dialkylzinc to diphenylphosphinoyl imines in the presence of chiral (3-amino alcohols with 85-87% ee [16] (Scheme 1.13). These three reports were, to the best of... 

KS Pang, M Rowland. Hepatic clearance of drugs. II. Experimental evidence for acceptance of the well-stirred model over the parallel tube model using lido-caine in the perfused rat liver in situ preparation. J Pharmacokin Biopharm 5/6 655— 699, 1977. 

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