Beilstein J. Org. Chem.2007,3, No. 11, doi:10.1186/1860-5397-3-11
] Other triazoloquinazolines were obtained from 2'-azidoacetophenone and as well as 2-azidobenzonitrile. [11] Quinazolines were also obtained in moderate yields by an intermolecular reductive N-heterocyclization of 2-nitro-benzaldehydes or 2-nitrophenyl ketones with formamide catalyzed by a combination of
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Graphical Abstract
Scheme 1:
Synthesis of triazoloquinazolinones 4a-dvia microwave irradiation.
Beilstein J. Org. Chem.2007,3, No. 5, doi:10.1186/1860-5397-3-5
diastereochemical outcome of the reaction, as observed before with the benzoxasilepines, [4] a selection of benzaldehydes with strongly (OMe) or weakly (OPiv) electron donating groups in ortho, meta and para positions were assayed (Table 1). Under the same experimental conditions used for the preparation of
. When the reaction is performed in CHCl3, a slight increase in the yields is observed, but the diastereoselection levels are basically the same.
We have also described that benzoxasilepines can be condensed with benzaldehydes in the presence of a stoichiometric amount of KF and 18-crown-6 and a
.
Reagents: i CH2 = CHCH2SiMe2Cl, Et3N, DCM, 85%; ii 2nd generation Grubbs catalyst, DCM, 91%.
Reagents: i: BF3·Et2O (1 eq), MeOH 95%; ii: substituted benzaldehydes, BF3·Et2O (1 eq), DCM; iii: substituted benzaldehydes, BF3·Et2O (2 eq), DCM; see Table 1 for cis/trans ratios and yields.
Reagents: i: a) OsO4
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Graphical Abstract
Scheme 1:
Retrosynthetic analysis for the homopterocarpan skeleton.