Solid State Oxidative Aromatization of Hantzsch 1,4‐Dihydropyridines to Pyridines Using Iodobenzene Diacetate or Hydroxy(tosyloxy)iodobenzene

Abstract

An easy, safe, solvent-free and effective method for oxidative aromatization of Hantzsch 1,4-dihydropyridines catalyzed by hypervalent iodine (IBD and HTIB) to corresponding pyridine derivatives in high yields within short span of time. All reactions were carried out just by grinding the two reactants.

An Expeditious Oxidative Aromatization of Hantzsch 1,4-Dihydropyridines to Pyridines Using Cetyltrimethylammonium Peroxodisulfate: A Phase Transferring Oxidant

“…In continuation to our work on aromatization of 1,4-DHP, 34,35 we report herein oxidation of 1,4-DHP to corresponding pyridine derivative using cetyltrimethylammonium peroxodisulfate, a phase transfer oxidant (Scheme 1). Results are summarized in Table 1.…”

“…4 These ubiquitous features always encourage synthetic chemist to explore improved protocols for the synthesis as well as the oxidation of 1,4-DHPs. A variety of reagents has been utilized for this oxidative conversion: S-nitrosoglutathion, 5 N2O4 complex of 18-crown-6, 6 photochemical oxidation, 7 Zr(NO3)4, 8 tetrakis-(pyridine)cobalt(II) dichromate, 9 nicotinum dichromate, 10 cytochrome P-450, 11 electrochemical catalysis, 12 urea nitrate, 13 peroxydisulfateCo(II), 13 Mn(OAc) 3 , 14 Vanadium salts, 15 tetra-n-butylammonium periodate, 16 AlCl3, 17 benzyltriphenylphosphonium peroxymonosulfate, 18 Mn(TPP)Cl-PSI/NaIO4, 19 [30][31][32][33][34][35] In spite of an overabundance of methods for this conversion, limitations like extended reaction times, poor yields and use of strong or toxic oxidant has led to the investigation of many alternative procedures.…”

Solvent-free synthesis and oxidative aromatization of diethyl-2,6-dimethyl-4-(1-phenyl-3-aryl-1H-pyrazol-4-yl)-1,4-dihydropyridine-3,5-dicarboxylates using hypervalent iodine (III) reagents

“…Encouraged by these observation and in continuation of our earlier studies on the oxidative aromatization of 1,4-DHP,s [39][40][41][42] and synthesis of biological active heterocyclic compounds [52][53] , we report herein, solvent free aromatization of diethyl 2, …”

Solvent‐Free One Pot Synthesis of 2‐aryl/Heteroarylbenzothiazoles Using Hypervalent Iodine (III) Reagents

“…Hypervalent iodine (III) reagents have gained much importance as an oxidizing reagent due to their environmentally benign properties and replacing the use of toxic transition metals involved in such processes [39, 40]. The poor solubility of hypervalent iodine (III) reagents in most common organic solvents led to the development of solvent‐free reactions [41, 42], which is demonstrated here.…”