Tetrasubstituted compounds

A wide range of organotin compounds can be manufactured and placed on the market. Commercially used organotins are characterized by the number of organic groups in the compound. Tetrasubstituted compounds... 

From TEEs unsubstituted, mono-, di-, tri-, and tetrasubstituted compounds were synthesized and investigated with third-harmonic generation [56] as well as electric field induced second-harmonic generation [67]. We here concentrate on the discussion of monomers of the most intriguing tetrasubstituted molecules and the symmetry dependence of their third-order nonlinearities [72]. Taking two donors and two acceptors three possible geometries can be realized (Fig. 23). The DDAA(cross)-TEE molecule has a mirror plane perpendicular to the y-axis, DDAA(ds)-TEE a mirror plane perpendicular to the x-axis, and DDAA(fra s)-TEE a two-fold rotation axis along z. 

The tetrasubstituted compound can only be attained with difficulty. The crude product is impure and has an irregular appearance. It can be purified with glacial acetic acid. 

For tetrasubstituted compounds of the type CRjR2R3R4 (Fig. 9) (1) if the molecule is planar, then three isomers are possible. (2) If the molecule is p3uramidal, then six isomers are possible. Each of the forms in Fig. 9, top, drawn as a pyramid, is not superimposable on its mirror image. Thus, three pairs of enantiomers are possible (one of which is shown in Fig. 9, middle). (3) If the molecule is tetrahedral, two isomers are possible, related to one another as object to mirror image. In actuality, only two tetrasubsti-tuted isomers of methane are known (pair of enantiomers). This is strong evidence for the tetrahedral model for the carbon atom. Similar reasoning leads to the same conclusion for trisubstituted methanes. 

UV spectral data110 166- 168, 170-112 175 an(j fluorescence-spectral properties166-168 for various pyrimido[5,4- ]pyrimidines have been reported. Tri- and tetrasubstituted pyrimido-[5,4- f]pyrimidinamines show intense absorption bands in the 280-340 nm region, and molar absorptivities of the tetrasubstituted compounds are generally larger than those of the trisub-stituted derivatives. The fluorescence spectra show emission maxima in the 435-547 nm region.168 Some UV data are summarized in Table 17. 

The amount of the 2, 4, 6-trinitro and N, 2, 4, 6-tetranitrocom-pounds should perhaps be added together in estimating the maximum possible percentage of C-substitution since the latter may be formed from the former. However, the ready reaction of nitronium ions with the N-methyl-N, 2, 4-trinitroaniline (exp. O) shows that this reaction (path d) is also a route to the tetrasubstituted compound. 

The 4-(3-methyl-2-butenyl)phloracylphenones and 4,4,6,6-tetrakis(3-methyl-2-butenyl)phloracylphenones are not present in hops, but they are accessible by synthesis. Thus 2-(3-methylbutanoyl)-4-(3-methyl-2-butenyl)phloroglucinol (178, Fig. 80) with a melting point of 140°C was obtained in 9% yieid as by-product in the preparation of humulone (42). The tetrasubstituted compounds are known as lupones. Thus, lupone with melting point 44°C (179, Fig. 80), coiupone with melting point 42 C (180, Fig. 80) and adlupone with melting point 45°C (181, Fig. 80) have been synthesized (53). 

Fig. 16 Preparation and reactions of diformyl[2.2]paracyclophanes. (a) formylation of dibromo [2.2]paracyclophanes (b) preparation of pseudogeminal diformyl[2.2]paracyclophane (c) Wittig and Bestmann-Ohira reactions of aldehydes to afford divinyl and diethynyl compounds, respectively (d) preparation of 4,5,12,13-substituted [2.2]paracyclophanes by Diels-Alder reaction between 1,2,4,5-hexatetrene and substituted alkynes (e) preparation of step tetrasubstituted compounds from 1,2-disubstituted ethynes...

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