| Heterocyclic compounds hold a special place in organic chemistry. Their role in drug design can not be overstated and the appearance of heterocyclic motifs in natural products is astronomically frequent. 1H-2,3-benzoxazines are much rarer and have received very little attention from the standpoint of both their preparation and their reactivity, which have the essential elements for activity. N-Acyliminium ions are important, reactive species in organic synthesis for the construction of carbon-carbon and carbon-heteroatom bonds. An efficient method to construct 1H-2,3-benzoxazines by Lewis acid-catalyzed N-acyliminium ions intramolecular reaction was described. According to the process already reported, the N-alkoxyphthalimides were prepared by the reactions of N-hydroxyphthalimide with arylmethyl halide or alcohol. They were treated with hydrazine in ethanol, then acylated with acid chlorides in the presence of sodium carbonate in a biphasic system to construct the hydroxamates.Reactions of hydroxamates with aldehydes in the presence of BF3·Et2O or TMSCl/NaI give 4-substituted 1H-2,3-benzoxazines in good yields through an N-acyl Pictet-Spengler mechanism. Although the Pictet-Spengler has been widely used in the following amine prototypes: dopamine/tyramine, tryptophan/tryptamine, histidine/histamine, to form the tetrahydroisoquinolines and tetrahydrocarbolines, application of hydroxamate was not as well documented. A series of 1H-2,3-benzoxazine derivatives were synthesized and characterized by NMR spectra, HRMS and X-ray.The rearrangement of 4-aryl 1H-2,3-benzoxazine derivatives was investigated. The reaction affords cyclic N-acyl hemiaminal derivatives under basic conditions, which convert to 1-arylisobenzofuran derivatives in the treatment of acid and be trapped by various dienophiles to afford skeletal congeners of 1-arylnaphthalene lignans. The new compounds were also characterized by NMR spectra and HRMS.
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