Methylene Green groups

A few nitro derivatives of methylene blue have been described. By introducing one nitro group under mild conditions (nitric acid of ca. 20% and sodium nitrite) methylene green was obtained [85]. 

In birds and amphibia, the green biliverdin IX is excreted in mammals, a soluble enzyme called biliverdin reductase reduces the methenyl bridge between pyrrole III and pyrrole IV to a methylene group to produce bilirubin, a yellow pigment (Figure 32-12). 

Fig. 6 Typical PET probes (a) and representative fluorescence light-up responses toward selected metal ions in tabulated (b) and graphical form (c trace 1 = 14, trace 2 = 14-(Zn2+)2, trace DMA = 9,10-dimethylanthracene in MeCN). Color code coordinating atoms in blue, atoms which take part in the complexation and show (main, in 14) PET activity in orange, fluorophore in green. Lincoln and co-workers have demonstrated that the attachment of two dimethylamino groups through propylene spacers to the 9,10-positions of anthracene has a more than 100-fold weaker PET activity than the attachment through methylene spacers [62]. The blue N atoms in 14 are thus predominantly responsible for coordination. For symbols, see Fig. 3. Quantum yield of 14 in MeCN estimated from intensity readings published in [61] and quantum yield data of the parent compound without active PET, DMA, published in [63]. (Reprinted in part with permission from [61]. Copyright 1988 American Chemical Society)...

The a- and y-methylene groups of pyrylium salts condense with pyranones and ben-zopyranones when the salts are heated in acetic anhydride or phosphorus oxychloride. Some of the resulting compounds are potentially interesting as dyes, for example the tripyran (110) (68JOC4418). In hot acetic anhydride equimolar amounts of the salt (111) and flavone condense to give a green-coloured salt (112) (78AP236). 

Only aldehydes with an a-methylene group (i, e., R—CH2CHO) condense with 3,5-diaminobenzoic acid to form quinaldines.92 Consequently, in the carbohydrate series only 2-desoxysugars will react. The usual procedure adopted is to add to the unknown sugar solution an equal volume of a 1.3 percent solution of 3,5-diaminobenzoic acid hydrochloride in 50 percent aqueous perchloric acid. If the carbohydrate solution contains a 2-desoxysugar it will assume a yellow color with a green fluorescence.93 Use of an ester instead of a salt of 3,5-diaminobenzoic acid reduces the sensitivity of the test. 

Supplementary support for the interpretation of the temperature-dependent dynamic H NMR spectra of 33 is presented by additional studies of (A,A,A,A)/(A,A,A,A)-[(EtNH3)4n Mg4(L12)6 ] (34). In 33 and 34, the methylene protons of the ligands exhibit identical VT NMR spectra. Moreover, the diastereotopic methylene protons (magenta) of the ethyl ammonium counterions of 34 display similar temperature-dependent coalescence as the ligand vinylether methylene protons (green). This is due to the fact that, even in solution, the ethyl ammonium groups are fixed to the tripodal calix-like surfaces of the [Mg4(L12)6]4 scaffold and therefore the methylene protons are in a chiral environment and display diastereotopicity. 

A large group of extraction-spectrophotometric methods, similar to the Rhodamine B method, is based on extraction of ion associates of AuCU with various basic dyes, such as Brilliant Green (toluene) [47 9], Methylene Blue (chloroform) [50-53], Nile Blue A [54], Chrompyrazole I (an antipyrine dye, formula 23.1) (toluene, e = 6.5-10 at 580 nm) [55]. 

Enamine constitutes an excellent example of A(1,2) strain. Because of the 8a < > 8b resonance involving overlap of lone pair of electrons on the nitrogen with the rt-bond, the bonds shown in green color in 8a are, more or less, in a single plane that brings the methylene group attached to the nitrogen atom and the substituent R, must it be equatorial, very close to each other to result in severe steric interactions. Consequently, the enamine 8a adopts a conformation wherein the substituent R occupies axial position [9-11]. 

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