Preparation of Novel Polycyclic Heterocycles Using a Tin(II) Chloride Dihydrate-Mediated Deacetalisation-Bicyclisation Sequence

Abstract

Tin(II) chloride dihydrate-mediated deacetalisationbicyclisation procedures for the construction of novel polycyclic heterocycles from amides possessing a pendant acetal group are reported. Optimisation and scoping studies are described; using this methodology, a range of known, and novel, ring-fused heterocyclic systems have been prepared, some in enantiomerically pure form.

From Tea to Health: Exploring Abrus mollis for Liver Protection and Unraveling Its Potential Mechanisms

“…The structures of known compounds ( 5 – 36 ) were confirmed to be formononetin ( 5 ), 8-methylretusin ( 6 ), 5,7,4′-trihydroxy-6,8-dimethoxyisoflavone ( 7 ), afromosin ( 8 ), 4,6,7-trimethoxyisoflavone ( 9 ), 2′-hydroxy-5′-methoxybiochanin A ( 10 ), 5,7,3′-trihydroxy-6,4′-dimethoxyisoflavone ( 11 ), pratensein ( 12 ), abrusprecatin A ( 13 ), (6a R ,11a R )-vesticarpan ( 14 ), abrusprecatin B ( 15 ), abrusprecatin C ( 16 ), medicarpin ( 17 ), (6a R , 11a R )-3-hydroxy-9,10-dimethoxy pterocarpan ( 18 ), (6a R ,11a R )-(−)-2-methoxymaackiain ( 19 ), 2­( S )-7,4′-dihydroxy-3′-methoxyflavanone ( 20 ), 2­( R )-liquirtigenin ( 21 ), 2­( R )-7-hydroxy-4′- methoxy dihydroflavones ( 22 ), isoliquiritigenin ( 23 ), 1-(2,4-dihydroxyphenyl)-3-(4-hydroxyphenyl)-propan-1-one ( 24 ), 4′- O -methyldavidigenin ( 25 ), (3 R )-2′,3′-dihydroxy-6,7,4′-trimethoxyisoflavane ( 26 ), pterosonins F ( 27 ), 2-(2′-methoxy,4′-hydroxy)-aryl-3-methyl-6-hydroxy benzofuran ( 28 ), (8 R ,8’ R )-(−)-trans-3,4-divanillyltetrahydrofuran ( 29 ), (8 R ,7’ S ,8’ R )-(+)-isoshonanin ( 30 ), (8 S )-2,4-dihydroxy-8-hydroxymethyl-4′-methoxydeoxybenzoin ( 31 ), 1 H -indole-3-carboxylic acid, methyl ester ( 32 ), 3,3a-dihydro-1 H -benzo­[ d ]­pyrrolo­[2,1- b ]­[1,3] oxazine-1,5­(2 H )-dione ( 33 ), 2,3,3a,5-tetrahydro-1 H -benzo­[ d ]­pyrrolo­[2,1- b ]­[1,3]­oxazin-1-one ( 34 ), N -[4′-hydroxy-( Z )-cinnamoyl]- l -tyrosine methyl ester ( 35 ), and N -[4′-hydroxy-( E )- cinnamoyl]- l -tyrosine methyl ester ( 36 ).…”

“…Furthermore, the characteristic coupling constants of J H-2 12.4, 2.7 Hz and J H-2 ″12.8, 3.0 Hz as well as the positive Cotton effect at 311 nm for 4 in the CD spectrum (Figure 3) further confirmed that its configuration was 2S, 2″S. 36,37 Then, its structure was finally elucidated and named mollisone D. The structures of known compounds (5−36) were confirmed to be formononetin (5), 38 8-methylretusin (6), 39 5,7,4′-trihydroxy-6,8-dimethoxyisoflavone (7), 40 afromosin (8), 41 4,6,7-trimethoxyisoflavone ( 9), 42 2′-hydroxy-5′-methoxybiochanin A (10), 43 5,7,3′-trihydroxy-6,4′-dimethoxyisoflavone (11), 44 pratensein (12), 45 abrusprecatin A (13), 35 (6aR,11aR)-vesticarpan ( 14), 34 abrusprecatin B (15), 35 abrusprecatin C ( 16), 35 medicarpin (17), 46 (6aR, 11aR)-3hydroxy-9,10-dimethoxy pterocarpan (18), 47 (6aR,11aR)-(−)-2-methoxymaackiain ( 19), 48 2(S)-7,4′-dihydroxy-3′-me- thoxyflavanone (20), 49 2(R)-liquirtigenin (21), 50 2(R)-7hydroxy-4′-methoxy dihydroflavones ( 22), 51 isoliquiritigenin (23), 52 1-(2,4-dihydroxyphenyl)-3-(4-hydroxyphenyl)-propan-1-one (24), 53 4′-O-methyldavidigenin (25), 54 (3R)-2′,3′dihydroxy-6,7,4′-trimethoxyisoflavane (26), 55 pterosonins F (27), 56 2-(2′-methoxy,4′-hydroxy)-aryl-3-methyl-6-hydroxy benzofuran (28), 57 (8R,8'R)-(−)-trans-3,4-divanillyltetrahydrofuran (29), 58 (8R,7'S,8'R)-(+)-isoshonanin (30), 59 (8S)-2,4-dihydroxy-8-hydroxymethyl-4′-methoxydeoxybenzoin (31), 60 1H-indole-3-carboxylic acid, methyl ester (32), 61 63 N-[4′-hydroxy-(Z)-cinnamoyl]-Ltyrosine methyl ester (35), 64 and N-[4′-hydroxy-(E)cinnamoyl]-L-tyrosine methyl ester (36)…”

Debenzylation or Demethylation in Methyl Ester of O‐Alkyl Nitrophenols with Stannous Chloride Dihydrate

“…We anticipated that depending on the reaction condition, the dealkylation might happen if an electron‐withdrawing group is present either at the ortho or para position of the O ‐alkyl group. The reagent has been used as a potential and inexpensive reagent in many chemical transformations, for example, cyclization, [6] multicomponent reactions, [7] preparation of heterocycles, [8] esterification, [9] etc. Many research groups reported nitro group reduction with stannous chloride dihydrate or with anhydrous form [10–13] .…”