Applications of Sulfated Tin Oxide (STO) in Organic Synthesis - from 2016 to 2021

Abstract

In this mini-review, authors have briefed about the applications of sulfated tin oxide (STO) as bifunctional catalyst in various C-C, C-hetero bond formations. Synthesis of biologically relevant pyranoquinolines, benzimidazoles, benzodiazepines, fully substituted pyridines, dihydropyridines and isoxazoles were performed by heterogeneous recyclable and reusable solid acid catalyst, STO. In addition, methodologies such as N-Boc protection of amines, production of renewable less viscous, high-density fuel molecules from α-pinene, selective production of MeCl from CH4, esterification, tert-butylation and conversion of glucose into value added 5-hydroxymethylfurfural, were established by using STO as catalyst. CONTENTS 1. Introduction 2. Recent applications of STO (During 2016-2021) 2-1. Synthesis of Heterocycles 2-1-1. Synthesis of 2-amino-4H-pyranoquinolines 2-1-2. Synthesis of 1,4-dihydropyridine derivatives 2-1-2-1. Varala and co-workers 2-1-2-2. Munde and co-workers 2-1-3. Synthesis of fully functionalized pyridines 2-1-4. Synthesis of benzimidazoles 2-1-5. Synthesis of 1,5-benzodiazepine derivatives 2-1-6. Synthesis of 4-arylmethylidene-3-substituted-isoxazol-5(4H)-ones 2-2. Miscellaneous reactions 2-2-1. Coupling reactions of α-pinene to produce dimeric hydrocarbon products (fuels) 2-2-2. N-Boc (N-tert-butoxycarbonyl) protection of aliphatic, aromatic and cyclic amines 2-2-3. Gas phase catalytic chlorination of CH4 2-2-4. Esterification of levulinic acid 2-2-5. Esterification of propionic acid 2-2-6. tert-Butylation of phenol 2-2-7. Esterification of free fatty acids (FFA) 2-2-8. Conversion of D-glucose to 5-hydroxymethylfurfural (HMF) 3. Conclusion

Synthesis of β-amino alcohols by ring opening of epoxides with amines catalyzed by sulfated tin oxide under mild and solvent-free conditions

“…Due to its low cost, greater stability, non-corrosive nature, reuse and recyclability, high efficiency, and large surface area, sulfated tin oxide (STO, SO4 -2 /SnO2) has emerged as an effective and commercial catalyst. It is used extensively in chemical and industrial applications, [29][30][31][32][33][34][35][36] consisting of both sulfated and sulfonic acid moiety on heterogeneous solid bases.…”