Reaction of ethyl azidoacetate with 6-formylchromans, followed by cyclisation of the azides obtained, leads to 1, 7, 8, 9-tetrahydropyrano [2, 3-g] indoles and 2, 3, 4, 8-tetrahydropyrano [3, 2-f] indoles. Some aspects of the chemical reactivity of these new tricyclic systems are
![1,7,8,9-tetrahydropyrano[2,3-g]indole-2-carboxylic acid结构式](https://image.chemsrc.com/caspic/417/81257-90-1.png)
![2,3,4,8-tetrahydropyrano[3,2-f]indole结构式](https://image.chemsrc.com/caspic/047/81258-15-3.png)
![1,7,8,9-tetrahydropyrano[2,3-g]indole结构式](https://image.chemsrc.com/caspic/303/81257-93-4.png)
![tetrahydro-1,7,8,9 pyranno[2,3-g]indolecarboxylate-2 de methyle结构式](https://image.chemsrc.com/caspic/358/81257-87-6.png)
![chloro-5 tetrahydro-1,7,8,9 pyranno[2,3-g]indolecarboxylate-2 de methyle结构式](https://image.chemsrc.com/caspic/320/81257-88-7.png)
![methoxy-5 tetrahydro-1,7,8,9 pyranno[2,3-g]indolecarboxylate-2 de methyle结构式](https://image.chemsrc.com/caspic/282/81257-89-8.png)
