On the reaction of N-vinyliminophosphoranes. Part 16. A new synthesis of 5H-indeno[1,2-b]pyridines and 5H-indeno[1,2-b]pyridin-5-ones

Abstract

Thermal react ion of tri bu tyl ( i nden -3yl i m i no) p hosp hora ne with ~l,punsaturated ketones and a Ide hydes led to a Michael-type C-C bond formation and subsequent aza-Wittig reaction to give 5H-indeno(l,2b)pyridines in good to modest yield. The products were oxidized conveniently by chromium trioxide and t-butyl hydroperoxide to give 5H-indeno[l,2-b] pyridin-5-ones, including the 4-azafluorenone alkaloid onyc h i ne.

N-Vinylic Phosphazenes. A Useful Tool for the Synthesis of Acyclic and Heterocyclic Compounds

“…Formation of pyridines 92 following this mechanism has been reported previously for the reaction of cyclohepta-1,3,5-trienylphosphazenes, derived from tributylphosphine [2g,40], hindered phosphazenes derived from tributylphosphine or triphenylphosphine, or -(methoxycarbonyl) and -(methoxycarbamoyl)vinylphosphazenes [14] with ,unsaturated aldehydes [41]. Formation of pyridines 92 following this mechanism has been reported previously for the reaction of cyclohepta-1,3,5-trienylphosphazenes, derived from tributylphosphine [2g,40], hindered phosphazenes derived from tributylphosphine or triphenylphosphine, or -(methoxycarbonyl) and -(methoxycarbamoyl)vinylphosphazenes [14] with ,unsaturated aldehydes [41].…”

Bioactive Azafluorenone Alkaloids from Polyalthia debilis (Pierre) Finet & Gagnep.

“…In 1976 the structure of natural onychine was assigned based on its UV, IR, 1 H-NMR and MS spectra as 1-aza-4-methyl-fluoren-9-one [3]. Later the synthesis of onychine was reported [10,11] and its structure was revised to 4-aza-1-methyl-fluoren-9-one [10]. To elucidate core structure of the revised azafluorenone, therefore, a series of related derivatives bearing methoxy group at 5-, 6-, 7- and 8-positions including 6,7-dimethoxyonychine was synthesized [12,13].…”

“…Elution with hexane-acetone gave 11 fractions of yellow oil and dark brown gum (C6.6.1-C6.6.11), the fractions eluted from hexane-acetone, 98:2 (C6.6.2 and C6.6.3) were further separated. Fraction C6.6.2 (6.6 mg of yellow oil) was chromatograhed on silica gel (1.5 g) eluting with hexane-acetone, 98:2 to give a yellow solid (1.5 mg) of compound 1 (1-methyl-4-azafluoren-9-one or onychine); mp 124-126 °C (lit mp 125-127°C [11], 125-129 °C [7], 133-135°C [10]; R f = 0.95 (hexane-acetone, 9:1); UV (EtOH) λ max (logε): 252 (4.16), 279 (3.87), 289 (3.88), 307 (3.42) nm; IR (UATR solid): υ max 2,925, 1,702, 1,596, 1,564, 1,448, 1,371, 756 cm -1 ; 1 H-NMR (acetone- d 6 ): δ 2.60 (d, 3H, J = 0.48 Hz, H-10), 7.14 (dd, 1H, J = 5.26, 0.48 Hz, H-2), 7.51(td, 1H, J = 7.43, 1.23 Hz, H-7), 7.66 (dd, 1H, J = 7.43, 1.23 Hz, H-8), 7.67 (td, 1H, J = 7.43, 1.23 Hz, H-6), 7.84 (dd, 1H, J = 7.43, 1.23 Hz, H-5), 8.45 (d, 1H, J = 5.26 Hz, H-3); 13 C-NMR (acetone- d 6 ): δ 16.8 (C-10), 121.3 (C-5), 123.9 (C-8), 126.2 (C-9a), 126.6 (C-2), 131.5 (C-7), 135.5 (C-8a), 135.7 (C-6), 143.9 (C-4b), 147.9 (C-1), 153.7 (C-3), 165.6 (C-4a), 193.2 (C-9); LRMS (EI): m/z (%) = 195 (72) [M] + , 167 (9), 166 (7), 139 (6); HRMS (TOF): m/z [M+H] + calcd. for C 13 H 10 NO:196.0761 found:196.0757.…”

Regioselective three‐component synthesis of novel indeno[1,2‐b]‐pyrazolo[4,3‐e]pyridines‐fused derivatives of 4‐azafluorenone alkaloid

“…As a result, the development of simple and efficient procedures to the synthesis of analogues of these alkaloids, containing indenopyridine scaffold, has attracted considerable attention [7]. [7]; direct cyclization of 2-aryl-3-methylpyridines to give 5H-indeno[1,2-b]pyridines followed by oxidation [7b]; cyclization of 2-aryl-3-nicotinic acids by the use of polyphosphoric acid [7b,8], or by extrusion of organophosphorus compounds [9]. However, even these methods are still not satisfactory in view of using toxic catalyst, narrow application scope of substrates, harsh reaction conditions, scarce generality and operational complexity due to the occurrence of several competitive side reactions.…”