Addition Of TFA Research Articles

Conjugated Macrocycles Related to the Porphyrins. Part 16.1 Synthesis of Hexa- and Heptaalkyl-Substituted Inverted or N-Confused Porphyrins by the “3 + 1” Methodology

Pyrrole-2,4-dicarboxaldehydes 13a−c were condensed with a tripyrrane dicarboxylic acid 12 in 1% TFA−CH2Cl2 to give, following oxidation with 0.1% FeCl3, a series of “etio-type” N-confused porphyrins 14a−c. Excellent yields were obtained when the diformylpyrrole possessed a 5-alkyl substituent, although the products were most easily isolated in the form of their hydrochloride salts. Addition of TFA to the free base inverted porphyrins led to initial protonation onto the external nitrogen atom to produce monocations 19 and further acidification afforded a dications 21. UV−vis spectroscopy showed strong Soret bands for 14, 19, and 21, features that are associated with fully aromatic porphyrinoid systems, and proton NMR spectroscopy confirmed the presence of powerful diamagnetic ring current where the meso-protons resonated near 10 ppm while the interior CH was strongly shielded to −6 ppm for the free base structures and −4 ppm for the dications 21. Taking into account the effect of the introduction of deloca...

Rhodium(II)-Catalyzed Decomposition of 1-Diazo-4-(1- or 2-naphthyl)-2-butanones as a New Route to Rearranged Pimarane and Abietane Skeleta. Synthesis of Umbrosone

The Rh2(OAc)4-catalyzed intramolecular Buchner reaction of 1-diazo-4-(1- or 2-naphthyl)butan-2-ones was examined as a potential route to abietane and rearranged abietane derivatives. Treatment of the α-diazo ketone 26 with catalytic amount of dirhodium tetraacetate in CH2Cl2 at 0 °C furnished the tetracyclic derivative 27 in good yield. Addition of TFA to 27 (in CH2Cl2) resulted in an acid-induced opening of the cyclopropane ring to give the 4a- and 10a-methyldihydrophenanthrenones 28 and 29 in nearly equal amounts. These compounds and their analogs appear to be suitable intermediates for the synthesis of diterpenoids containing aromatic A or C rings. When the diazo ketone 34 was decomposed under Rh(II) catalysis, a 10-methyldihydroanthracenone (i.e., 36) was obtained as the main product, besides minor amounts of the expected tetracyclic ketone 35. The extension of this result to the preparation of the methoxy-substituted dihydroanthracenone 39 (52% yield) was exploited in a new total synthesis of umbroso...

Protonation of the porphyrin-ketones and their complexes: Verification of spectral forms and mechanisms

Protomeric forms of the porphyrin-ketones (or oxo-chlorins) are investigated by optical spectral methods. The main spectral forms of octaethylporphine-ketone and coproporphyrin-ketone tetramethyl ester appearing in organic solvents in the presence of trifluoroacetic acid, in SDS micellar solution and in sulfuric acid, namely, the free base, monocation, dication and trication, are identified and described in detail. Their mutual transformations are shown to proceed differently for the two dyes. The possibility of protonation of the macrocycle is also proven for the porphyrin-ketone complexes. Two new spectral forms of platinum(II) and palladium(II) complexes of the porphyrinketones appearing in organic solvents on addition of TFA are described. Possible mechanisms of protonation, including formation of oxonium ions and carbocations, are discussed for these dyes.

ChemInform Abstract: Mechanism of the Nucleophilic Addition to 2,3‐Dihydrodipyrrin‐1(10H)‐ones.

AbstractStarting from any of compounds (II)‐(V) and MeOH (I), addition of TFA leads to an equilibrium mixture (after ca. 100 h) of (Z)‐(II), addition product (III), tautomer (IV), and (E)‐isomer (V) in the ratio 25:35:35:5.

ChemInform Abstract: Electrophilic Capture by “Conjugated” Bis(bicyclo(1.1.0)butanes). Site Specificity of the Initiation Step and Thermodynamic Control of the Ensuing Electronic Reorganization.

AbstractAddition of TFA to the bis(bicyclobutane) (I) yields the tetracyclic trifluoroacetate (IIa), whose structure is identified after saponification to the alcohol (IIb) by an X‐ray analysis (no data given).

Mass Spectra of Butyl Esters and N-Trifluoroacetyl Butyl Esters of Some Iminodicarboxylic Acids upon Electron Impact

Abstract Mass spectra (electron impact at 20 eV) of butyl esters and N-trifluoroacetyl (TFA) butyl esters of some iminodicarboxylic acids (IDCAs) were determined by gas chromatography-mass spectrometry. The IDCAs included iminodiacetic acid (1), 2-(carboxymethylamino)propionic acid (2), 3-(carboxymethylamino)propionic acid (3), 2,2′-iminodipropionic acid (4), 2,3′-iminodipropionic acid (5), 3,3′-iminodipropionic acid (6), N-methyliminodiacetic acid (7), and nitrilotriacetic acid (8). The mass spectra of the butyl ester derivatives are simple, exhibiting the corresponding molecular (M+) ions with the exception of 5. The α,α′-IDCAs (1, 2, 4, 7, and 8) are characterized by M+, M −101 (COOC4H9) (base peak), and M −157 (COOC4H9+C4H8) ions. The β,β′-IDCA (6) is characterized by a more complex spectrum with M+, M −73 (OC4H9), M −115 (CH2COOC4H9) (base peak), M −129 (OC4H9+C4H9), and M −171 (CH2COOC4H9+C4H9) ions. The α,β′-IDCAs (3 and 5) in general show spectra in which both ions characteristic of α,α′- and β,β′-IDCAs are observed. The addition of TFA to the imino nitrogens of 1–6 increases complexity of the resulting spectra. In these instances, although M+ ions are usually present, neither M −101 nor M −115 ions are base peaks. The fragmentation pathways of these two volatile derivatives of the IDCAs upon electron impact are discussed.