Divergent reactivity in tandem reduction–Michael ring closures of five‐ and six‐membered cyclic enones

Abstract

in Wiley InterScience (www.interscience.wiley.com).In this study, methyl (AE)-1-(2-nitrobenzyl)-4-oxo-2-cyclohexene-1-carboxylate and methyl (AE)-(2-nitrobenzyl)-4-oxo-2-cyclopentene-1-carboxylate were prepared and subjected to reductive cyclization under dissolving metal conditions. The two reactants showed divergent behavior with the six-ring substrate reacting at the ester carbonyl and the five-ring substrate closing on the enone double bond. The difference in reactivity is attributed to the conformational flexibility, relative reactivity, and steric environment of C4-substituted six-and five-membered cyclic enones.

Advances in the Chemistry of Tetrahydroquinolines

“…The 2-nitro-substituted substrates 119 reacted with 6 equivalents of iron powder in glacial acetic acid to afford tetrahydroquinoline derivatives 120 in high yields through a reductive cyclization. Recently the same group extended their methodology for the synthesis of fused and spiro-tetrahydroquinolines 123 and 124 starting from nitro compounds 121 and 122 (Scheme ) . The cyclohexenone derivative 121 did not afford the expected reduction-Michael adduct, and instead the spiro compound 123 was isolated in 95% yield.…”

Tin(ii) chloride dihydrate/choline chloride deep eutectic solvent: redox properties in the fast synthesis of N-arylacetamides and indolo(pyrrolo)[1,2-a]quinoxalines

“…[7][8][9] They are also fundamental building blocks employed in the synthesis of amines which are obtained by the reduction of the nitro group through metalacid combinations, catalytic hydrogenation, hydride transfer reductions, catalytic transfer hydrogenation and metal-free reduction methods. 10 The synthetic utility of this transformation is highlighted in several one pot procedures for the obtention of diverse structures including imines, amides 11 and a-aminophosphonates 12 together with heterocyclic compounds such as benzimidazoles, [13][14][15] quinazolinones, 16,17 pyrrolines, 18 isoindolinone derivatives, 19 tetrahydroquinolines, [20][21][22][23] and quinoxalines, 24,25 where a tandem one-pot reduction and intramolecular cyclization reaction is achieved.…”

New conditions for synthesis of (±)‐2‐monosubstituted and (±)‐2,2‐disubstituted 2,3‐dihydro‐4(1H)‐quinazolinones from 2‐nitro‐ and 2‐aminobenzamide

“…We have previously utilized tandem reactions initiated by dissolving metal reduction of nitroarenes to prepare indole‐3‐carboxylic esters [ 10] and benzo‐fused oxepinones, diazepinones, [ 11] and carbazoles [ 12] as well as various linear‐fused ring systems [ 13]. In this project, we have used a tandem reduction‐condensative cyclization strategy involving 2‐nitrobenzamide ( 1 ) and aldehydes 2a , 2b , 2c , 2d , 2e , 2f , 2g , 2h or ketones 2i , 2j , 2k , 2l , 2m , 2n , 2o for the formation of 2‐monosubstituted and 2,2‐disubstituted 2,3‐dihydro‐4(1 H )‐quinazolinones 3 .…”