Subject substituted derivatives

The acidic properties of sulphonamides and their mono-substitution derivatives are particularly well illustrated in the alkyl ubstitution compounds, which by reason of these properties can be prepared by two distinct methods. Thus mono- and di-ethylamine, when subjected to the Schotten-Baumann reaction using benzenesulphonyl chloride, gi e benzenesulphonethylamide, and bcnzenesulphondiethylamide respectively. These compounds can also... 

In this section three main aspects will be considered. Firstly, the basic strengths of the principal heterocyclic systems under review and the effects of structural modification on this parameter will be discussed. For reference some pK values are collected in Table 3. Secondly, the position of protonation in these carbon-protonating systems will be considered. Thirdly, the reactivity aspects of protonation are mentioned. Protonation yields in most cases highly reactive electrophilic species. Under conditions in which both protonated and non-protonated base co-exist, polymerization frequently occurs. Further ipso protonation of substituted derivatives may induce rearrangement, and also the protonated heterocycles are found to be subject to ring-opening attack by nucleophilic reagents. 

Platinum(II) isocyanide complexes of the general formulas [PtL4], [PtL3X], and PtL2X2 and substituted derivatives thereof (L = RNC, X = halogen, H, R, etc.), have been studied recently and will be the main subjects of discussion. It may be observed that much work on complexes of the first and third molecular stoichiometries had been reported previously. 

The preparation of biologically active [l,2,4]triazolo[l,5- ]pyrazines has been reported recently. The reaction routes are shown in Scheme 50. Dowling et al. reported <2005BML4809> the synthesis of aryl-substituted derivatives 411. The first step was the transformation of the 2-aminopyrazine compound 409 to an amidine 410, which was subjected... 

The intermediate tricyclic ketones 495 and 496 have been transformed to the methoxy-substituted derivative 97284,285) latter ketone is subject to hydrogen-deuterium exchange only under basic conditions and appears to exist entirely in the keto form despite the ready formation of its anion and successful methylation on oxygen . In agreement with the aromatic nature of 490, the hydrocarbon undergoes electrophilic substitution reactions... 

In some cases, steric interactions can prevent unimolecular reactions. Tetrahe-drane (18) has been the subject of a number of studies, and the conclusion is that, if formed, it would rapidly decompose to form two molecules of acetylene. However, tetra-tert-butyltetrahedrane (19) is a quite stable substance, and on heating rearranges to tetra-tert-butylcyclobutadiene. An orbital symmetry " analysis of the cleavage of tetrahedrane to acetylene indicates that it involves a torsional motion that in the case of the tert-butyl substituted derivative would bring the tert-butyl groups very close to each other. As a result, this mode of reaction is not possible, and the compound is relatively stable. 

A variety of substituted derivatives of arsenane, antimonane and bisminane are known, although the parent compound has only been reported for arsenane. They are prepared by similar routes to those used for the arsolanes and stibolanes and are listed in Table 3. Of these, 1-methylarsenane (76JA3778) and 1-methylantimonane (76JOM(110)183) have recently been the subject of NMR studies. 

Quinazolines are of great interest in the pharmaceutical industry as protein tyrosine kinase inhibitors. Dener et al 8 described a synthesis starting from 2-methoxybenzaldehyde, Wang, or Rink resins. With the aldehyde resin reductive aminations were undertaken to yield polymer-bound secondary amines (Fig. 7). The latter were subjected to 2,4-dichloro-6,7-dimethoxyquinazoline to give the 4-amino-substituted derivatives. These were then allowed to react with primary or secondary amines at 135-140° in the presence of DBU in DMA. As a result of a detailed scope and limitation study, Dener et al,28 note that some bifunctional amines, such as piperazine, give to some extent dimeric derivatives. 

The combination of dithiolene and diimine chelating ligands in square-planar ds complexes gives rise to a unique CT excited state, and complexes of this class have been the subject of a rich and growing amount of research in recent years. The Pt(diimine)(dithiolene) complexes were among the earliest examples of emission from square-planar metal complexes in fluid solution. Luminescence from room temperature solutions of Pt(diimine)(mnt) complexes with diimine = bpy, phen, or an alkyl- or aryl-substituted derivative was reported in 1990 by Zuleta et al. (98, 99), following an initial report on similar complexes with a 1,1-dithiolate. 

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