Indoles spiro 4//-pyran

On replacing 2-hydroxynaphthalene-l,4-dione (21) by 4-hydroxy-6-methyl-2H-pyran-2-one (11), Bazgir and his group obtained another series of spiro[indole-3,4 -pyrano[4,3-li]pyran]-3 -carbonitriles (23) under the same reaction conditions they even synthesized these scaffolds using magnetically recoverable and reusable CuFe204 nanoparticles as well in aqueous media (Scheme 12) [112,113], Besides, sodium stearate was also efficiently used in S5mthesiz-ing this spirooxindole scaffold in aqueous micellar media [114],... 

The research group of Bazgir [112,113] also reported the S5mthesis of a series of diverse spiro[indole-3,8 -phenaleno[l,2-l ]pyran]-9 -carbonitriles 25 in good yields from the one-pot, three-component cyclocondensation reaction of 3-hydroxy-IH-phenalen-l-one (24), malononitrile (3), and substituted isatins (20) in refluxing aqueous media using the same catalysts (Scheme 13). 

SCHEME 12 Synthesis of spiro[indole-3,4 -pyrano[4,3-fc]pyran]-3 -carbonitriles 23 [112—114], p-TSA, p-toluenesulfomc add. 

SCHEME 13 Synthesis of spiro[indole-3,8 -phenaleno[l,2-6]pyran]-9-carbonitriles 25 [112,113], p-TSA, p-toluenesulfonic add. 

R. Ghahremanzadeh, T. Amanpour, A. Bazgir, Clean synthesis of spiro[indole-3,8 -phenaleno[l,2-i ]pyran]-9-carbonitriles and spiropndole-3,4 -pyrano[4,3-i)]pyran]-3-carbonitriles by one-pot, three-component reactions, J. Heterocyclic Chem. 47 (2010) 46-49. 

Catalyst 3 was also used in the construction of substituted 3-hydroxy-2-oxindoles by the reaction of 5-methoxy substituted isatins with various indoles [28]. Up to 91% ee could be obtained in 1,4-dioxane as the solvent and benzoic acid as an additive. Similarly, 3 was apphed as catalyst for the formation of spiro[4H-pyran-3,3 -oxindoles] via a one-pot domino Knoevenagel, conjugate addition, cyclization sequence (Scheme 6.12) [29]. 

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