Heterocyclisch [c]‐anellierte Cumarine aus 4‐Azido‐3‐cumarincarbaldehyden

Abstract

Heterocyclic [c]‐Condensed Coumarins from 4‐Azido‐3‐coumarincarbaldehydes 4‐Azido‐3‐coumarincarbaldehydes 2a–d are useful starting materials for syntheses of a variety of 3,4‐disubstituted coumarins as well as heterocyclic [c]‐fused coumarins, e. g. isoxazoles, pyrazoles and 1,5‐diazepines, under mild conditions. In these reactions, 2a–d are – despite of their thermolability — superior to the corresponding 4‐chloro‐3‐coumarincarbaldehydes 1a–d, from which they were prepared. An improved method for the preparation of 1a–d from 4‐hydroxy‐coumarins is described.

Synthesis of aromatic and heteroaromatic annelated [1,4]diazepines

“…Steinführer and al. 3 proved that the reaction mixture contained a mixture of 4-chlor-3-coumarincarbaldehyde 2 (65%) with 4-chlorocoumarin as a side product (20%).…”

“…We studied three procedures described in the literature: chloroformylation of 1 carried out with an equimolecular mixture of POCl 3 and DMF in trichlorethylene (yield = 97%) 2 or in chloroform (65%) 3 or in a mixture of POCl 3 and excess of DMF (85%). 4 Literature 2,4 claims high yields of carbaldehyde 2 and 4-chlorocoumarin without any indication of their ratio.…”

“…In comparable reaction times, we could at room temperature achieve better yields (up to 87%) than those described in the literature. 3 The compounds 3 could be separated from the reaction mixture by simple filtration. Steinführer and coll.…”

“…The reaction between azidocarbaldehyde 3 and diamines 4−7 was tested as possible route to the title 1,4-diazepines 9−12. Under reaction conditions described in literature 3 (DMF, 4 h, method A), followed by column chromatography and crystallization from acetonitrile, pure compounds 9−12 were obtained (Scheme 1).…”

Synthesis of some new biologically active coumarin derivatives

“…The possibility that diamines might further react inter-or intramolecularly [9][10][11] at either of the two carbonyl groups prompted us to examine the interaction of aromatic diamines with compound 2. The reactions of equimolar amounts of dione 2 and 4-phenylenediamine or 4-aminothiophenol were carried out by refluxing in toluene for 4 h (Scheme 3).…”