Synthesis of Pyrido-Fused Quinazolinone Derivatives via Copper-Catalyzed Domino Reaction
A simple and efficient synthesis of 11H-pyrido[2,1-b]quinazolin-11-ones by Cu(OAc)2·H2O-catalyzed reaction of easily available substituted isatins and 2-bromopyridine derivatives has been developed. The reaction involves C-N/C-C bond cleavage and two C-N bond formations in a one-pot operation. This methodology is complementary to previously reported synthetic procedures, and two plausible reaction mechanisms are discussed. (Chemical Equation Presented).
Copper-catalyzed aerobic oxidative annulation and carbon-carbon bond cleavage of arylacetamides: Domino synthesis of fused quinazolinones
An efficient copper-catalyzed tandem aerobic oxidative annulation and carbon-carbon bond cleavage reaction was developed from easily accessible arylacetamides, which provides a direct approach for the domino synthesis of a vast array of tricyclic or tetracyclic fused quinazolinone alkaloid structures. A plausible reaction mechanism is proposed involving an aerobic benzylic oxidation/ cyclization/decarbonylation cascade.
Sun, Jie,Tan, Qitao,Yang, Wusong,Liu, Bingxin,Xu, Bin
p. 388 - 394
(2014/05/20)
Synthesis of α-carbolines starting from 2,3-dichloropyridines and substituted anilines
9H-α-Carbolines have been prepared via consecutive intermolecular Buchwald-Hartwig reaction and Pd-catalyzed intramolecular direct arylation from commercially available 2,3-dichloropyridines and substituted anilines. The combination of a high reaction temperature (180°C) and the use of DBU were found to be crucial for the intramolecular direct arylation reactions of the 3-chloro-N-phenylpyridin-2-amines as no reaction was observed at 120°C and 180°C using different inorganic and other organic bases. On the other hand, nitrogen-methylated pyridine analogues of these substrates {N-[3-chloro-1- methylpyridin-2(1H)-ylidene]anilines} do undergo ring closure at 120°C, with K3PO4 as base, affording the respective 1-methyl-1H-α-carbolines in good yields.
Hostyn, Steven,Van Baelen, Gitte,Lemiere, Guy L. F.,Maes, Bert U. W.
supporting information; scheme or table
p. 2653 - 2660
(2009/08/14)
2,1-Benzisothiazoles. XIII . Intermediates and Products in the Sulfur Extrusion Reaction of 2,1-Benzisothiazolines-3(1H)-one. A New Synthesis of 11H-Pyridoquinazolin-11-one ("Pyracridone")
Triethyl phosphite abstracts sulfur from 2,1-benzisothiazolin-3(1H)-one (1); a reaction intermediate is the spirocyclic compound 11, and products include the benzoxazine 6 and polyanthraniloyl compounds.In the presence of pyridine, pyracridone (13) is formed.The ketene-imine 9 is probably not an intermediate in these reactions.The reactions of other nucleophiles with 1 and with its N-methyl derivative 15, have been examined.