Synthesis of [1]Benzopyrano[4,3-b]pyrrol-4(1H)-ones from 4-Chlorocoumarin

An Overview of the Synthesis of 3,4-Fused Pyrrolocoumarins of Biological Interest

“…Alberola et al prepared [1] benzopyrano[4,3- b ]pyrrol-4(1 H )-ones 17a , b , 49a – e from 4-acylamino- or 4-ketalaminocoumarin derivatives 48a – h under different conditions using acetic acid/water, or Me 3 SiI in chloroform or TiCl 4 in dichloromethane (DCM) or EtONa in ethanol or silica gel in chloroform [ 84 ]. Compounds 49a – e were prepared in high yields of 71–92% through the method with acetic acid/water.…”

“…Thermal elimination of phenylsulfenic acid from the intermediate dihydropyrrole derivative 44 followed by oxidation in the reaction conditions resulted in the final product 45 (Scheme 15). Alberola et al prepared [1] benzopyrano [4,3-b]pyrrol-4(1H)-ones 17a,b, 49a-e from 4-acylamino-or 4-ketalaminocoumarin derivatives 48a-h under different conditions using acetic acid/water, or Me3SiI in chloroform or TiCl4 in dichloromethane (DCM) or EtONa in ethanol or silica gel in chloroform [84]. Compounds 49a-e were prepared in high yields of 71-92% through the method with acetic acid/water.…”

Synthetic Routes to Coumarin(Benzopyrone)-Fused Five-Membered Aromatic Heterocycles Built on the α-Pyrone Moiety. Part 1: Five-Membered Aromatic Rings with One Heteroatom

“…Albrola et al indicated the preparation of N( α )-(2-oxo-2 H -l-benzopyran-4-yl)Weinreb-α-aminoamides 75 from 4-chlorocoumarin ( 73 ) and different α-aminoacids 74 . The reaction of 75 with various organometallic compounds, followed by cyclization, led to the formation of [l]benzopyrano[4,3- b ]pyrrol-4-ones 76 ( Scheme 22 ) [ 74 , 75 ].…”

AlCl3-catalyzed chemoselective cascade reactions of 4-anilinocoumarins with 2-furylcarbinols: access to densely functionalized chromeno[4,3-b]pyrrol-4(1H)-one derivatives

“…Due to their enormous biological and photophysical importance, several approaches for the synthesis of chromeno[4,3- b ]pyrrol-4(1 H )-ones have been developed. Among them, the conventional methods toward these heterocyclic scaffolds usually start with 4-substituted coumarins 3 (chloro, 3 a – c , e , g hydroxy, 3 d , g alkoxy group 3 b or amino 3 g , f ) and α-amino derivatives. They generally entail two-stage processes, conjugate addition–elimination at the 4-position of coumarins with subsequent annulation (often taking place with concomitant dehydration), affording the desired products.…”