Ring-opening hydrolysis of spiro-epoxyoxindoles using a reusable sulfonic acid functionalized nitrogen rich carbon catalyst

Abstract

Catalytic synthesis of vicinal diols via ring-opening hydrolysis of spiro-epoxyoxindoles.

Regioselective Ring-Opening of Spiro-Epoxyoxindoles by a Dual-Ligand Zinc-Based Metal–Organic Framework as an Efficient Heterogeneous Catalyst

“…The nucleophilic ring-opening of spiro-epoxyoxindoles has emerged as an attractive approach due to its end-product 3,3′-disubstituted oxindoles, which are widely distributed and have great significance as structural subunits of bioactive natural products and pharmaceuticals. , Particularly, 3-substituted-3-hydroxyoxindoles are powerful building blocks for drug discovery due to their wide range of biological activities depending on C-3 substitution. Intrigued by these promising therapeutic activities of 3-substituted-3-hydroxyoxindoles, many homogeneous and heterogeneous catalysts were reported for the nucleophilic ring-opening of spiro-epoxyoxindoles. − However, to the best of our knowledge, there is no report in the literature on the MOF-catalyzed nucleophilic ring-opening of spiro-epoxyoxindoles to synthesize 3-substituted-3-hydroxyoxindoles. Accordingly, we were enthused to evaluate the catalytic efficiency of ADES- 6 in the nucleophilic ring-opening of spiro-epoxyoxindoles to achieve 3-substituted-3-hydroxyoxindoles (Scheme ).…”

Metal‐Free Ring‐Opening of Epoxides

“…al. [108] developed a metalfree catalytic system for the hydrolysis of spiro-epoxyoxindoles (250). Here they explored the catalytic ability of a nitrogen-rich sulfonated carbon as a catalyst derived from a cucurbit [6]uril (CB 6 ) based molecule.…”

“…Recently in 2021, Subramanian et. al [108] . developed a metal‐free catalytic system for the hydrolysis of spiro‐epoxyoxindoles ( 250 ).…”

“…Lower catalytic activity of salt (107) (12 % yield) was attributed to the planarity of the sp 2 -centered imidazoline scaffold leading to better delocalization of the positive charge which rendered it poor hydrogen bond donor, whereas salt (110) gave lesser yield of only 38 % due to the larger steric environment around the amidinium unit next to the nitrogen atoms. Catalyst (108) provided the ring opening product in good yield of 78 % which could be justified by the special geometry of 7-membered 1,3diazepinium cations which did not allow the planar conformation to be adopted, thus the positive charge is less delocalized over the NCN atoms of imidazole scaffold (Scheme 33).…”