Anlagerung von Ketonen an Nitroaromaten

Abstract

Die Umsetzung des Adduktes IIc aus 1.3.5-Trinitro-benzol, Aceton und Alkali mit Natriumborbydrid fuhrt zur Reduktion der Carbonylgruppe und Anlagerung von Hydridionen an den aromatischen Kern. Das so gebildete Salz VI geht bei der Einwirkung von Brom unter Riickoxydation des Kerns und Abspaltung einer Nitrogruppe in 4.QDinitro-2-methyl-cumaran (VII) iiber. Analoge Umsetzungen von I mit Cyclohexanon, Cyclopentanon und Acetophenon ergaben die Verbindungen XIV, XV und XVI. Nach den grundlegenden Untenuchungen von J. MEISENHEIMER~), die sptiter ergiinzt wurdens), reagiert 1.3.5-Trinitro-benzol (I) mit Kaliumtithylat zu einem Addukt der Struktur Ha. 1 I IIa-c J a: R = OC&., c: R = CH+2O-CHS, Kat@ = Na@ oder K8 Kat@= K@@ b: R = N' \ I Kat' = HaN= Die Ergebnisse der Titration von I mit Natrium-[p-amino-Bthylat] in khylendiamin fiihrten H. BROCKMANN~) zu der Annahme, daO Verbindungen des Typs I1 weitere Alkoholat-Anionen an die im Kern verbliebenen Doppelbindungen anzulagern vermagen. Auch aus Aminen und

Some aspects of anionic .sigma.-complexes

“…TNB also gives rise to a Janovsky a complex 80 isolated by Kimura163 and Gitis.149 Its structure was established by UV and IR spectroscopy as well as chemically, i.e., by analysis of products of its oxidation by hydrogen peroxide163 and reduction by sodium borohydride. 164,165 The first reaction leads to 2,4,6-trinitrobenzyl methyl ketone, the second to 4,6-dinitro-2-methyl-2,3-dihydrobenzofuran. The structure of 80 was proven by 1H NMR spectroscopy166 and confirmed by X-ray diffraction analysis167 as well as by 13C NMR spectroscopy;25 the fluorescence spectra of this complex were also investigated.168…”

Nucleophilic Dearomatizing (DNAr) Reactions of Aromatic C,H-Systems. A Mature Paradigm in Organic Synthesis

“…The same authors found that oxidizing the analogous complexes 551 with 2 equiv of NBS results in the formation of the tricyclic isoxazoline N -oxides 552 , probably through bromination at the carbon adjacent to the carbonyl linkage and subsequent displacement of bromide ion by intramolecular attack of the oxygen of the nitronate moiety close to the electrophilic center ). , …”

“…237 Increasing the electrophilicity of the ring as in symtrinitrobenzene (TNB) 465 promotes the complete reduction of the aromatic system by the action of sodium borohydride, affording 1,3,5-trinitrocyclohexanes 467 and 468 as mixture of stereoisomers. The reaction proceeds via successive addition of hydride to the ring of the nitro compound and quenching of the trisodium salt 466 with tartaric acid 237 and bromine, 242 respectively (Scheme 72). First reported by Severin and Schmitz, the synthetic applications of the process were further developed mostly by Atroshchenko et al 243 Curiously, the analogous reduction of symmetrical trinitrobenzenes 469 containing one or two additional electronwithdrawing substituents furnished 1,3,5-trinitrocyclohexane 467 as the only isolable product (Scheme 72).…”

Synthesis of benzannelated five-membered heteroaromatic compounds from 2,4,6-trinitrotoluene

“…TNB is a multi-purpose synthon, including use for the synthesis of polyfunctional benzannelated heterocycles. [8][9][10][11] TNB is prepared by decarboxylation of 2,4,6-trinitrobenzoic acid. 5,12 The TNT methyl group is CH-active and able to condense with various aromatic electrophiles, predominantly in the presence of bases (TNT acidity: pK a H 2 O = 13.6; pK a CH 3 OH =15.6; pK a DMSO = 10.5).…”