Reaction of ethyl azidoacetate with 6-formyl-4 chromanones, followed by cyclization of the azides obtained leads to 7, 8-dihydropyrano [2, 3-g] indol-9 (1 H)-one. One aspect of the chemical reactivity of these new tricyclic systems is described. The structure of the compounds isolated from various syntheses is established by proton nmr data.
![methoxy-5 oxo-9 dihydro-7,8 pyranno[2,3-g]indolecarboxylate-2 de methyle结构式](https://image.chemsrc.com/caspic/340/81258-03-9.png)
![methyl 5-methoxy-7,8-dihydro-1H-spiro[pyrano[2,3-g]indole-9,2'-[1,3]dioxolane]-2-carboxylate结构式](https://image.chemsrc.com/caspic/416/81258-01-7.png)
![5-methoxy-7,8-dihydro-1H-pyrano[2,3-g]indol-9-one结构式](https://image.chemsrc.com/caspic/178/81258-07-3.png)