Aryliminopropadienone−C-Amidoketenimine− Amidinoketene−2-Aminoquinolone Cascades and the Ynamine−Isocyanate Reaction

Abstract

Imidoylketenes 11 and oxoketenimines 12 are generated by flash vacuum thermolysis of Meldrum's acid derivatives 9, pyrrolediones 17 and 18, and triazole 19 and are observed by IR spectroscopy. Ketenimine-3-carboxylic acid esters 12a are isolable at room temperature. Ketenes 11 and ketenimines 12 undergo rapid interconversion in the gas phase, and the ketenes cyclize to 4-quinolones 13. When using an amine leaving group in Meldrum's acid derivatives 9c, the major reaction products are aryliminopropadienones, ArN=C=C=C=O (15). The latter react with 1 equiv of nucleophile to produce ketenimines 12 and with 2 equiv to afford malonic acid imide derivatives 16. N-Arylketenimine-C-carboxamides 12c cyclize to quinolones 13c via the transient amidinoketenes 11c at temperatures of 25-40 degrees C. This implies rapid interconversion of ketenes and ketenimines by a 1,3-shift of the dimethylamino group, even at room temperature. This interconversion explains previously poorly understood outcomes of the ynamine-isocyanate reaction. The solvent dependence of the tautomerism of 4-quinolones/4-quinolinols is discussed. Rotational barriers of NMe(2) groups in amidoketenimines 12c and malonioc amides and amidines 16 (24) are reported.

Reaction of Iminopropadienones with Amines: Mechanistic Explanations of Zwitterionic Intermediate, Ketene and Ketenimine Formation

“…[1][2][3][4] These unusual cumulenes have been characterized by IR and NMR spectroscopy [1][2][3][4][5] as well as by their chemical reactions. Iminopropadienones 4 undergo a multitude of nucleophilic addition reactions; with bisnucleophiles, cyclization leads to a variety of heterocyclic compounds containing 5-, 6-, 7-, 8-, and 9-membered rings.…”

Flash‐Vakuumpyrolyse – Techniken und Reaktionen

“…[67] Unter FVP-Bedingungen lassen sich Carbazole rein und in exzellenter Ausbeute erhalten [Gl. [68] Die Bildung von Iminopropadienonen aus 31 bei hçheren Te mperaturen ist in Gleichung (39) in Abschnitt 5.4 gezeigt. [58] Tr iazole 29 kçnnen ebenfalls zur Generierung von Keteniminen eingesetzt werden, welche die gründlich untersuchte a-Oxoketenimin-a-Imidoylketen-Umlagerung (32Ð33)e ingehen kçnnen (Schema 5).…”

2(3H)Pyrrolone – A Biologically Active Scaffold (A Review)

“…1H-pyrrol-3-(2H)-ones. Its mechanism was investigated by Brown and Eastwood 57 and more recently by Wentrum et al 49 . …”

“…Such double p-p * cotton effects are observed at 250 nm in a saturated imides 43 and result from the transitions involving combinations of the carbonyl n orbitals of opposite symmetry. This cotton effect however is much smaller than the n-p* cotton effects caused primarily by the a,b-unsaturated lactam chromophore [49][50][51][52] . …”