146535-52-6Relevant articles and documents
Oxidative [3+3] Annulation of Atropaldehyde Acetals with 1,3-Bisnucleophiles: An Efficient Method of Constructing Six-Membered Aromatic Rings, Including Salicylates and Carbazoles
Gu, Yanlong,Wu, Fengtian,Yang, Jian
, p. 2727 - 2741 (2018/07/29)
An oxidative [3+3] annulation of atropaldehyde acetals with various 1,3-bisnucleophiles was developed using either N-bromosuccinimide or copper(II) bromide as oxidizing reagent and Br?nsted or Lewis acids as catalyst. The [3+3] annulations can be considered mechanistically as oxidizing reagent-induced acid-acid-catalyzed domino reactions established through the concept of auto-tandem catalysis. Alkyl acetoacetates, α-(indol-2-yl)acetate, anilines, 1-methyl-1H-pyrazol-3-amine, ethyl 5-amino-1H-pyrazole-3-carboxylate, and 3-amino-1H-indazole can all be used as 1,3-bisnucleophiles in this type of transformation. The established reactions can very efficiently construct six-membered aromatic rings, including salicylates and carbazoles. A four-step method of synthesizing the anti-inflammatory agent diflunisal was also developed based on the oxidative [3+3] annulation reaction, and the yield was high. (Figure presented.).
Concerning the mechanism of the Friedlaender quinoline synthesis
Muchowski, Joseph M.,Maddox, Michael L.
, p. 461 - 478 (2007/10/03)
Detailed experiments regarding the mechanism of the Friedlaender synthesis of quinolines from o-amino-benzaldehydes and simple aldehydes or ketones are described. Under the basic or acidic conditions commonly used in this reaction, it is concluded that the first step involves a slow intermolecular aldol condensation of the aldehyde or ketone with the o-aminobenzaldehyde. The aldol adduct 5 generated in this manner then undergoes very rapid cyclization to 4, which subsequently loses water to produce the quinoline derivative 8. Both 5 and 4 are too short lived to be detectable (TLC), even when deliberately generated by other means. It is also shown that E-enones corresponding to 6, i.e., the aldol dehydration product, are converted into quinolines (e.g., 21a and 21b from 17a and 17b) under basic or acidic conditions. Such enones are not detected as intermediates in the base-induced Friedlaender synthesis, even though certain congeners (17b) would be easily observable. Under acidic conditions these enones are too short lived to be detectable. Schiff bases derived from 2-aminobenzaldehyde (18a) and aldehydes or ketones can be generated under special conditions, but they show reactivity patterns different from those seen in the usual Friedlaender condensations. Thus, the ytterbium-triflate-catalyzed reaction of aldehydes with 18a at room temperature in toluene generates the E-Schiff bases (33, R1 = H), from which isomeric mixtures of tetrahydroquinoline derivatives 26 are formed exclusively. At higher temperatures, the E-Schiff bases 33 are isomerized to the Z-Schiff bases 34, from which the 3-substituted quinoline derivatives 24 are formed as the major products under appropriate conditions. Also, the ytterbium-triflate-catalyzed reaction of 18a with the pyrrolidine enamines of the methyl-n-alkylketones 38a,b produces mixtures in which the 2-monosubstituted kinetic products 37b,d predominate over the 2,3-disubstituted thermodynamic products 21c,e by a factor of 4:1 to 5:1. These results are opposite to those observed under the usual basic or acidic Friedlaender reactions with methyl-n-alkylketones, where the thermodynamic products are usually strongly favored. The unusual kinetic:thermodynamic product ratios observed with 38a,b are ascribed to the generation and rapid cyclization of mixtures of the Schiff bases 35 and 36, in which the kinetic isomer 35 is highly predominant.
BIS MONO- AND BICYCLIC ARYL AND HETEROARYL COMPOUNDS WHICH INHIBIT EGF AND/OR PDGF RECEPTOR TYROSINE KINASE
-
, (2008/06/13)
-
