Synthesis of Novel Spiro[Cyclopropane-Indazole] Derivatives Via Magnesium-Mediated Conjugate Addition of Bromoform

Substrate-oriented selectivity in the Mg-mediated conjugate addition of bromoform to electron-deficient alkenes

The Mg-mediated conjugate addition of bromoform to a variety of electron-deficient alkenes has been investigated. In the case of nitrodienes and dibenzylideneacetones, tribromomethylated products were isolated, whereas spiro-cyclopropanated products were obtained with cyclic dibenzylideneketones and 3-olefinic oxindoles. The spiro-cyclopropyl ketones derived from cyclic dibenzylideneketones were successfully transformed into fused furans via the Cloke-Wilson rearrangement.

Synthesis of Spiro Indazole-Tetrahydrothiophenes via Sulfa-Michael/Aldol Cascade Reactions

The sulfa-Michael/aldol cascade reaction of 5-arylmethylidene-1-phenyl-6,7-dihydro-1H-indazol-4(5H)-ones and 1,4-dithiane-2,5-diol yielded novel 2′-(4-aryl)-4′-hydroxy-1-phenyl-4′,5′,6,7-tetrahydro-2′H-spiro[indazole-5,3′-thiophen]-4(1H)-ones in moderate yields. The structures of all the products were characterised thoroughly by NMR, IR and HRMS, together with X-ray crystallographic analysis.

Synthesis of novel dispiro[indazole-5,3′-pyrrolidine-2′,3″-indole] derivatives via 1,3-dipolar cycloaddition of azomethine ylide

The 1,3-dipolar cycloaddition of azomethine ylide, generated in situ from isatin and sarcosine, to 5-arylmethylidene-1-phenyl-6,7-dihydro-1 H-indazol-4(5 H)-ones afforded novel 1′-methyl-4′-aryl-1-phenyl-6,7-dihydrodispiro[indazole-5,3′-pyrrolidine-2′,3″-indole]-2″,4(1 H,1″ H)-diones in moderate yields. The structures of all the products were characterised thoroughly by NMR, IR, HRMS, together with X-ray crystallographic analysis.