Heteropoly acid-catalyzed aza-Prins-cyclization: an expeditious synthesis of 4-hydroxypiperidines

A detailed investigation of the aza-Prins reaction

“…24 In 2005, Armstrong et al reported an aza-Prins-pinacol approach to 7-azabicyclo[2.2.1]heptanes 25, 26 but it was not until 2006 that Martín et al 27,28 reported the first study devoted specifically to developing an aza-Prins reaction, in the conventional sense of a Prins reaction, and followed this with a catalytic version in 2009. 29 More recently, Yadav et al have also reported that BiCl 3 , 30 GaI 3 /I 2 31 and heteropoly acids 32 (such as phosphomolybdic acid) will also promote aza-Prins type reactions. In 2007, Shimizu et al reported that olefins and acetylenes, in the presence of titanium tetraiodide and iodine, underwent an aza-Prins-type reaction to yield 1,3-iodoamines.…”

Highly Efficient Direct Synthesis of Scaffold 9a,10,12,12a‐Tetrahydrobenzo[b]cyclopenta[f]pyrrolo[1,2‐d][1,4]diazepinone by Using Active Phoshomolybdic Acid

“…Over the past few decades, high catalytic activity, economic viability, easy availability, nontoxicity, and greener nature made phosphomolybdic acid (PMA) and PMA‐supported catalysts as a promising and selective reagent for the synthetic transformations , especially in synthesis of α‐aminophosphonates , bridged 1,2,4,5‐tetraoxanes , 4,4′‐(arylmethylene)bis(1 H ‐pyrazol‐5‐ols) , homoallylic amines , tetrahedropyranylation , dehydration of alcohols , Friedel–Crafts reactions , aza‐Diels–Alder reactions , aziridinization of olefins , and ring opening of aziridines . Inspired by the synthetic applicability of PMA as an efficient catalyst for organic transformations, we herein report an efficient synthetic protocol for the synthesis of pyrrole[1,2‐ d ] benzodiazepines by using PMA as a non‐corrosive, less toxic , less expensive, easily available, and potent greener solid catalyst. However, to the best of our knowledge, PMA is not used as a catalyst for synthesis of 9a,10,12,12a‐tetrahydrobenzo[ b ]cyclopenta[ f ]pyrrolo[1,2‐ d ][1,4]diazepinone to date.…”

Water‐Mediated Synthesis of Anthelmintic Piperidinols and Their Molecular Docking Studies

“…In addition, they act as sodium and calcium channel blockers, estrogen receptor modulators, liver glycogen phosphorylase inhibitors, map kinase inhibitors and dopamine D2 receptor antagonist . The traditional routes for synthesis of piperidinols involve gold mediated chemoselective reduction of amide followed by Ferrier rearrangement, silica chloride catalyzed and ultrasound assisted reduction of 4‐piperidinone, NaBH(OAc) 2 assisted reaction of aldehydes with amines, enzymatic transformation of trans‐6‐aminocyclohept‐3‐enols, phosphomolybdic acid mediated aza‐Prins‐cyclization and solid phase synthesis from 1,2,3,6‐tetrahydro‐pyridines . Most of these methods suffer from drawbacks such as tedious workup procedure, harsh reaction conditions, prolonged reaction time, unsatisfactory yields and use of strongly basic conditions.…”