Anilines molecular ions

Interestingly, the three isomeric aminopyridine molecular ions display ion chemistry similar to aniline molecular ions, i.e., metastable HNC loss, [222] instead of HCN loss which should also be possible due to the pyridine core of the molecule (Fig. 6.56b). 

FIGURE 10.12 A consecutive photodissociation sequence observed in an experiment with a single aniline molecular ion being the initial reactant. (Reproduced from Hpjbjerre, K. Offenberg, D. Bisgaard, C.Z. Stapelfeldt, H. Staanum, P.F. Mortensen, A. Diewsen, M. Phys. Rev. A. 2008, 77, 030702(R). With permission from the American Physical Society.)... 

This technique has, for example, shown that HNC rather than HCN is lost from metastable aniline molecular ions and that ionized methyl acetate loses CH20H radicals rather than OCHj as the lowest-energy fragmentation route. 

B-trichloro-N-triphenylborazine, mp 290-292°C, was obtained in 86 yield following the procedure of Groszos and StafieJ (6). This material was then transformed into B-triamino-N-triphenyl-borazine in 67 yield using the method of Toeniskoetter and Hall (2)- B-trianilinoborazine and the novel B-tris[di(trimethylsilyl)-amlno]borazlne (mp, 131.5-132°C characterized by GC/MS, molecular ion 558 amu, and elemental analysis) were synthesized in 76 and 71 yields, respectively, by interaction of aniline and hexamethyl-disllazane with chloroborazine in the presence of triethylamine. 

Fig. 6.56. El mass spectra of aniline (a) and 2-aminopyridine (b). Different in mechanism from the N-heterocycles, but very similar in appearance the aromatic amine molecular ions eliminate HNC. Spectra used by permission of NIST. NIST 2002.

Hop, C.E.C.A. Dakubu, M. Holmes, J.L. Do the Aminopyridine Molecular Ions Display Aniline- or Pyridine-Type Behavior Org. Mass Spectrom. 1988, 23, 609-612. 

Aromatic Amines (Anilines) The molecular ion peak (odd number) of an aromatic monoamine is intense. Loss of one of the amino H atoms of aniline... 

Many other aliphatic or aromatic amines produce the same reaction. However if N-alkyl (or aryl)2-aniline is made to react with tris-dimethylaminophosphine, tricoordinated phosphorus compounds are obtained. Their analyses and mass spectra show that they are tetramers (5) when the energy of the ionizing electron beam is nearly 70 eV the mass spectra of the oligomers show an intense [M] peak which corresponds to the monomer ion (n = 1) but when the spectra are obtained by field desorption m.s. the molecular ion peak corresponds to a tetramer (n = 4) one sees also smaller peaks for ions n = 3, 2 or 1. 

Aromatic Amines (Anilines). The molecular ion peak (odd number) of an aromatic monoamine is intense. Loss of one of the amino H atoms of aniline gives a moderately intense M - 1 peak loss of a neutral molecule of HCN followed by loss of a hydrogen atom gives prominent peaks at mlz 66 and 65, respectively. 

Figure 3 shows the 70 eV EI-MS of the isomeric hydroxyanilines. Unlike the methoxy anilines, for which ortho, para and meta effects are quite pronounced, the EI-MS of these three positional isomers are very similar. The most abundant ion in the EI-MS of the hydroxyanilines is the molecular ion of m/z 109 whereas, by far the most prominent fragment ion is that of m/z 80, viz. [M — CO — H]+. A substantial contribution of the keto tautomer is suggested for the CO loss process38,42,43, as represented in Scheme 7 for the ortho isomer, and this tautomer may account for the weak positional effects. 

Aromatic amines show intense molecular ion peaks. A moderately intense peak may appear at an mie value one mass unit less than that of the molecular ion, due to loss of a hydrogen atom. The fragmentation of aromatic amines can be illustrated for the case of aniline ... 

By zero kinetic energy (ZEKE) PE spectroscopy a value of 7.7206 0.0002 eV has been determined for the first adiabatic IP of aniline. This technique makes it possible to obtain accurate and detailed information about molecular ions. 

What isotope peak intensities are expected for the molecular ions of aniline (CgHyN), acetophenone (CjHjO), ethyl iodide (C2H5I), and ethylamine (C2H7N) ... 

A series of experiments with the aniline ion (C6H5NH2+) illustrates the application of the SCSl-MS technique to complex molecular systems and demonstrates that it is possible to study consecutive photodissociation of molecular ions at the single ion level in an ion trap [33]. In addition to providing detailed information on fragmentation processes, such consecutive dissociation processes provide also a probabilistic way of preparing a wealth of single molecular ions that could be objects for further study or serve as reactant ions in other experiments. 

The conversion of furan acid 9 to the drug candidate 1 is straightforward (Scheme 7). The aniline side chain is installed via the mixed anhydride, and the activated fiiran is converted to the pyrrole by treatment with NH4OAC in hot N-methylpyrrolidinone (NMP). The latter reaction benefits from a particularly efficient work-up addition of water to the warm NMP solution induces crystallization of the product, which is filtered directly from the reaction mixture. HPLC purities of >98% are typical from this reaction, and the product can be recrystallized if further purification is needed. We struggled with one impurity, which was present at levels between 0.5-1.0% in the crude product recrystallization reduced the level to 0.3-0.5%. We initially did not Imow the identity of this impurity, other than by mass spectral analysis, which indicated a molecular ion of M+NH (1 has formula C17H17FN2O3, the impurity is... 

The first widely used intermediates for nucleophilic aromatic substitution were the aryl diazonium salts. Aryl diazonium ions are usually prepared by reaction of an aniline with nitrous acid, which is generated in situ from a nitrite salt.81 Unlike aliphatic diazonium ions, which decompose very rapidly to molecular nitrogen and a carbocation (see Part A, Section 4.1.5), aryl diazonium ions are stable enough to exist in solution at room temperature and below. They can also be isolated as salts with nonnucleophilic anions, such as tetrafluoroborate or trifluoroacetate.82 Salts prepared with 0-benzenedisulfonimidate also appear to have potential for synthetic application.83... 

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