From fragments

This approach is important for the synthesis of cinnolines. CHEC(1984) 1984CHEC(2)1 already covered several examples. The methodology used starts with an aniline ortho substituted with an alkene (Widman-Stoermer type), alkyne (Richter type), or enolisable ketone (Borsche type) which is diazotisized, delivering the sixth atom, allowing cyclization. CHEC-II(1996) 1996CHEC-II(6)1 gave more examples. 

Dibenzo[f,. ]cinnolines 259 have been obtained from 2-naphthylanilines 258 via diazotization followed by intramolecular electrophilic aromatic substitution (Equation 65) 2003BMC1475 . 

This category covers the major approaches to pyridazines and phthalazines, particularly reaction of hydrazines with 1,4-dicarbonyl compounds or their equivalents, but also the synthesis of (benzo)-pyridazines by [2 -H 4] cycloaddition reactions using azo or diazo dienophiles, and was thoroughly 

1 -Tetralone-8-carboxylic acid, an example of a cis unsaturated 1,4-dicarbonyl compound, cyclizes with phenylhydrazine to give 2,7,8,9-tetrahydro-2-phenyl-3//-benzo[ 7e]cinnolin-3-one in over 90% yield 81S59 . 

The use of precursors which allow aromatization by elimination after cyclization avoids the need for a separate oxidation step and has been exploited in several approaches to pyridazine derivatives. Thus, cyclization of hydroxy 4-keto acids with hydrazine and subsequent elimination of water allows direct access to pyridazinones and this approach, developed for the industrial preparation of 

Similarly, condensation of hydrazines with 4-aryl-2-hydroxy-2-(substituted-phenacyl)butanoic 

6-Diaryl-4,5-dihydro-3(2//)-pyridazinones with differently substituted aryl rings are available by condensation of hydrazines with 2,4-diaryl-4-oxobutanoic acids (Equation (35)) made from chalcones by addition of hydrogen cyanide followed by hydrolysis 88JHC799 . 

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As in the case of thiazole and the alkylthiazoles, cleavage of the thiazole ring takes place at the 1,2 and 3,4 bonds, confirmed by a metastable peak. The other important peaks result from fragmentation of thiirenium ion, in the case of 4- and 5-phenylthiazole and of the phenyl ring. These latter are generally present in the spectra of all comptmnds with benzene-ring substituents, they occur at m/e 77, 76, 75, 51, 50, 39 (124). The ion m/e 45 (HCS" ) is always present. 

LEAPEROG generates new leads from fragments Tripos... 

From Fragments Providing [2+n] Ring Atoms S.03.3.2.1 By two displacement reactions... 

In conclusion, SSIMS spectra provide not only evidence of all the elements present, but also detailed insight into molecular composition. Quasimolecular ions can be desorbed intact up to 15000 amu, depending on the particular molecule [3.17] and on whether an effective mechanism of ionization is present. Larger molecules can be identified from fragment peak patterns which are characteristic of the particular molecules. If the identity of the material being analyzed is completely unknown, spectral interpretation can be accomplished by comparing the major peaks in the spectrum with those in a library of standard spectra. 

C [22, 28] (equation 10) Nitrogen-free perfluoro compounds such as perfluorocyclohcxene, perfluorocyclohcxane, perfluoromethylcyclohexane, and perfluoroheptane result from fragmentation [22, 28]... 

Moore s equation was derived from fragments accelerated from high explosives packed in a casing. Baum (1984) showed, in comparing different models, that the Moore equation tends to follow the theoretical upper-velocity limit for high scaled energies. 

This appendix is a summary of the woiit published in the so-called Green Book (1989). Possible effects of explosions on humans include blast-wave overpressure effects, explosion-wind effects, impact from fragments and debris, collapse of buildings, and heat-radiation effects. Heat-radiation effects ate not treated here see Chapter 6, Figure 6.10 and Table 6.6. 

FIGURE 11.33 Restricdon mapping of a DNA molecule as determined by an analysis of the electrophoretic pattern obtained for different restriction endonuclease digests. (Keep in mind that a dsDNA molecule has a unique nucleotide sequence and therefore a definite polarity thus, fragments from one end are distinctly different from fragments derived from the other end.)... 

Imine formation by reaction of aniline 58 and dione 49 under thermal conditions gave a mixture of imines. Cyclodehydration using PPA gave nearly a 1 1 mixture of isomers 59 and 60. These authors attempted thermal cyclization conditions (similar to Gould-Jacobs type conditions) to affect cyclization of this mixture and failed. Also, these authors reported difficulty in the clean formation of the imine. They observed large amounts of the A -acetyl compound presumably coming from fragmentation of the imine at the reported temperature... 

An example of how information from fragmentation patterns can be used to solve structural problems is given in Worked Example 12.1. This example is a simple one, but the principles used are broadly applicable for organic structure determination by mass spectrometry. We ll see in the next section and in later chapters that specific functional groups, such as alcohols, ketones, aldehydes, and amines, show specific kinds of mass spectral fragmentations that can be interpreted to provide structural information. 

This closeness of 0 to zero explains the existence of a gas-oversaturated solution area in the polymer melt, when P < Pg, but the entire volume of gas remains in the solution. The degree of oversaturation, particularly upon free foaming (not in flow) can be 2- to 3-fold. In real polymer compositions, there are always solid admixtures, which have poor wetting areas. This reduces the degree of oversaturation at the interface melt-molding tool. Moreover, bubble nuclei can result from fragmentation of gas bubbles in the polymer [16]. Another factor that promotes the formation of bubble nuclei is the presence of localized hot points in the polymer melt they act as nuc-leation centres. Hot points appear either after a chemical reaction in the melt polymer [17], or in overheated areas on the surface of metal equipment [18]. Density of nucleation can be improved via introduction of various agents that reduce tension of the polymer [19]. 

The origin of these radical species is also not known. It is often considered that they may result from recoil, either from the original molecule or from fragments of other molecules following collision Perhaps the most commonly assumed, and the most likely, source of free radicals is radiolysis of the target compound The pre-... 

Simons KT, Kooperberg C, Huang E, Baker D. Assembly of protein tertiary structures from fragments with similar local sequences using simulated annealing and Bayesian scoring functions. J Mol Biol 1997 268 209-25. 

When dmg regulatory responsibilities are divided, there is no unity of command over dmg regulatory functions. The missing links resulting from fragmentation and delegation... 

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