A new versatile strategy involving a sequential four-component reaction of the nitroketene dithioacetals, alkylamine/benzylamine, isatin and various enolizable active methylene structures (pyrazolone, barbituric acid, 1,3-indandione and 2-hydroxy-1,4-naphthoquinone) as precursors under mild and catalyst-free conditions results in the synthesis of new functionalized spirooxindole pyrans named spiro[indoline-3,4 0pyrano[2,3-c]pyrazol], spiro[indoline-3,5 0 -pyrano[2,3-d]pyrimidine], spiro[indeno[1,2-b]pyran-4,3 0indoline] and spiro[benzo[g]chromene-4,3 0 -indoline] in moderate to good yields. The use of various active methylene compounds affords a range of skeletally distinct spirooxindole-based heterocycles with potential biological properties. The present strategy has many advantages, such as convenient one-pot operation, simple workup procedures and straightforward isolation without using tedious purification steps such as column chromatography, progress under catalyst-free condition and high molecular diversity. ; Tel: +98 28 33780040 † Electronic supplementary information (ESI) available. See Scheme 1 Synthesis of spiro(indoline-3,4 0 -pyrano[2,3-c]pyrazol)-2-one derivatives catalyzed by indium trichloride. Scheme 2 The one-pot, multi-component synthesis of bis-spirooxindoles in PEG-400/K 2 CO 3 at room temperature. 16526 | RSC Adv., 2019, 9, 16525-16533 This journal is Scheme 3 Synthetic approaches for the formation of spiro[indoline-3,4 0 -pyrano[2,3-c]pyrazol], spiro[indoline-3,5 0 -pyrano[2,3-d]pyrimidine], spiro[indeno[1,2-b]pyran-4,3 0 -indoline] and spiro[benzo[g]chromene-4,3 0 -indoline] (5a-q).Scheme 4 A plausible mechanism for the formation of 5 in catalyst-free conditions.This journal is
