Examples conversion

Alkyne alkylation is not limited to acetylene itself. Any terminal alkyne can be converted into its corresponding anion and then alkylated by treatment with an alkyl halide, yielding an internal alkyne. For example, conversion of 1-hexyne into its anion, followed by reaction with 1-bromobutane, yields 5-decyne. 

Increased levels of cytosolic calcium could potentiate ischaemia-reperfusion injury in several ways. For example, conversion of xanthine dehydrogenase to xanthine oxidase may be catalysed by a calcium-dependent protease (McCord, 1985). However, because it has been so difficult to demonstrate the presence of xanthine... 

As C-Br bond formation occurs by back-side attack, inversion of the configuration at carbon is anticipated. However, both racemization and rearrangement are observed as competing processes.10 For example, conversion of 2-butanol to 2-butyl bromide with PBr3 is accompanied by 10-13% racemization and a small... 

In Section 8.2.3.2, we discussed arylation of enolates and enolate equivalents using palladium catalysts. Related palladium-phosphine combinations are very effective catalysts for aromatic nucleophilic substitution reactions. For example, conversion of aryl iodides to nitriles can be done under mild conditions with Pd(PPh3)4 as a catalyst. 

Some enzymes have been found to be capable of conversion of the polyaromatic sulfur heterocycles in mixtures of an aqueous phase containing buffer+water-miscible solvent and a water-immiscible solvent. For example, conversion of thiophenes and sulfides was demonstrated in an aqueous system with 20% acetonitrile in contact with 0.2% diesel. A process for sulfur removal was designed based on this reaction [394], Additional details were given in Section 4.2.1. In a subsequent study effect of this system on PAH... 

Formation of these dinuclear mercury derivatives is accompanied by a red shift of the absorbance of the bis(alk-ynyl) backbone. For example, conversion of 2,7-bis(alkynyl)fluorene into the corresponding bis(methylmercury) derivative 50 leads to a shift of the main absorption band of the bis(alkynyl) backbone from 505 to 567 nm. Similar results have been obtained for 51-56.67 68... 

The location of a graph s peak (if there is one) depends on the base rate of the taxon that is, the proportion of taxon members in the overall sample. A base rate of. 50 (half of individuals are taxon members) produces a centered peak low base rates (common in psychopathology research) produce right-shifted peaks, such as those in the depression example. Conversely,... 

Some interesting modifications with respect to the base-induced isomerization have recently been developed. For example, conversion of 4-hydroxy-l-thiophenyl-2-alkynes 299 into the corresponding 4-hydroxy-substituted thiophenylallenes 300 was achieved by treatment with potassium hexamethyldisilazide at low temperature (Scheme 8.79) [165], If the hydroxyl group is protected as the THP ether an elimination reaction occurred, resulting in the formation of an enyne instead of allene 300. 

For example, conversion of the hexacoordinate (octahedral) derivatives [MnHCl(PP3)] to the corresponding deprotonated pentacoordinate (trigonal-bipyramidal or square pyramidal) derivatives [MnCl(PP3)]+ (M = Fe, Ru, Os), Scheme 6, follows electrode mechanisms that are more or less complicated depending upon the nature of the central metal.16... 

For example, conversion after two hours reaction time (T=70°C, p(H2/CO) = 50 bar) dropped from 99% in the absence of CO2 to 66.4% at a density d(C02) = 0.35 g mL to 0% at d(C02) = 0.57 g mL The observation of a yellow-orange solid precipitated during the addition of CO2 confirmed the efficient separation of catalyst and substrate. The same separation was induced in the product mixture if CO2 was introduced after the hydroformylation was completed. The mixture of regioisomeric nonanals formed during the reaction was extracted quantitatively with SCCO2 leaving an active hydroformylation catalyst behind in the reactor. 

The reaction of 2- and 4-pyridones, fused as part of a variety of 6,6-heterocyclic systems, is a recurring theme in many publications for example, conversion of diethyl 4-oxo-l,5,7,8-tetrahydro-4//-[l,6]naphthyridine 3,6-dicarboxy-late into the 4-chloro derivative <2004BML3441>, and others will appear through the chapter. 

Obviously, conversion of an acyclic diastereomer into a compound with known configuration is another secure method. For example, conversion of ester 3 into the ethenyl lactone324 which was hydrogenated to the known lactone (3.S,4A)-3-ethyltetrahydro-3,4-dimcthyl-2//-pyran-2-one... 

As another example, conversion to furnish either DC or AC, or combinations of either, at whatever frequencies are required, is easily accomplished by standard conversion techniques and add-on systems. 

Because of the low incident radiant flux (some 10 5 Einstein h l cm 2)t conversions below 1 % were obtained with pure alcohols after illuminating for 10 h, despite reasonable quantum yields. However, high chemical yields could be obtained for comparable numbers of photons and of molecules to transformed, i.e. with diluted solutions. For example, conversions of 50 or - 80 were found after 2 or 6 h, respectively, with 6 x 10 mol citronellol in 10 cm n-heptane, using a 125 W Hg-lamp. 

Disubstituted cyclopentane-1,3-diones and cyclohexane-1,3-diones were used as substrates. After formation of the aldol adducts subsequent intramolecular dehydration furnished products of types 94 and 96. The asymmetric intramolecular aldol reaction proceeds with a broad variety of natural amino acids as organocata-lysts. Among these L-proline was usually found to be the most versatile. For example, conversion of the 2,2-disubstituted cyclopentane-1,3-dione 93 in the presence of L-proline gave the desired product 94 in 86.6% yield and with enantioselectivity of 84% ee [97]. This example and a related reaction with a 2,2-disubstituted cyclohexane-1,3-dione 95 are shown in Scheme 6.42. Chiral induction depends... 

Transversion mutations convert purines to pyrimidines or vice-versa. For example, conversion of an A-T base pair to a T-A or C-G base pair is a transversion. Ultraviolet light can cause transversions, although not exclusively. Frameshift mutations result from the insertion or deletion of a single base pair. These are often due to planar intercalating mutagens, which insert into the double helix. More extensive deletions and insertions are common events, as shown in Figure 8-13. 

A few isolated examples104 172 187 147 prior to 1998 showed that organolithiums 427 tethered to aromatic rings can on occasion cyclise, apparently by nucleophilic addition of the organolithium to the Ti-system of the aromatic ring. In some cases (for example, the conversion of 194 to 196 or 298 to 299),104147 the organolithium 428 rearomatises to yield a new benzo-fused compound 429 in others (for example, conversion of 374 to 376, or 431 to 432 below),172 187 protonation yields a stable, dearomatised bicyclic product 430 or an isomer. 

The IBX approach to oxazolidinones is readily adaptable to the synthesis of amino sugars (Scheme 93) (00AGE2525, 02JA2233). For example, conversion of the dihydropyranyl alcohol 318 to the carbamate derivative... 

It is noteworthy that in practice even the reverse of the above may occur. Often it is necessary to analyse compounds that are too volatile. Significant losses during the preliminary treatment of the sample (e.g., extraction, removal of the solvent), due to this volatility, may introduce errors into the quantitative evaluation. Analysis of volatile carboxylic acids in biological samples is an example. Conversion of these compounds into less volatile derivatives is therefore advantageous from the viewpoint of both GC proper and preliminary isolation of the compounds and sample treatment. 

EXAMPLE Conversion of ferf-butyl alcohol to fe/T-butyl bromide. 

Both in situ infrared and multinuclear NMR under less severe conditions have been used to gain mechanistic insights. For the hydroformylation of 3,3-dimethyl but-l-ene, the formation and hydrogenolysis of the acylrhodium species Rh(C()R)(C())4( R=CH2CH2Bur) can be clearly seen by IR. NMR spectroscopy has also been very useful in the characterization of species that are very similar to the proposed catalytic intermediates. We have already seen (Section 2.3.3, Fig. 2.7) NMR evidence for equilibrium between a rhodium alkyl and the corresponding hydrido-alkene complex. There are many other similar examples. Conversion of 5.3 to 5.4 is therefore well precedented. In the absence of dihydrogen allowing CO and alkene to react with 5.1, CO adducts of species like 5.6 can be seen by NMR. Structures 5.11 and 5.12 are two examples where the alkenes used are 1-octene and styrene, respectively. 

Babel [http //openbabel.sourceforge.net/]), it is important to keep in mind the limitations of each format. For example, conversion from SMILES, which does not store atom coordinates, into Mobile would result either in the molecule having undefined geometry or the geometry being supplied by the conversion tool, which might be completely different from the real one. 

Nucleophilic substitution of chlorine is a key feature of a synthetic approach to a series of indole-6-carboxylic acids. For example, conversion of the starting nitrobenzene 392 using an SnAc reaction followed by reductive cyclization into the indole 393 was concluded by treatment with base to afford the final product 394 (Scheme 46) <2004SL883>. 

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