Studies on Benzodiazepinooxazoles. IV. The Formation of Quinolones by the Ring Contraction of a Benzo [6, 7]-1, 4-diazepino [5, 4-b]-oxazole Derivative

Abstract

Treatmentof 10-chloro-2,3,5,6,7,11b-hexahydro-7-methyl-11b-phenylbenzo [6,7] -1,4-diazepino [5,4-b]oxazol-6-one (IV) with sodium hydride in dimethyl acetamide gave the two compounds, 6-chloro-3-(2-hydroxyethyl)-1-methyl-4-phenyl-2(1H)-quinolone (V) and 6-chloro-3-hydroxy-1-methyl-4-pherryl-2(1H)-quinolone (VI). A mechanistic assumption for the formation of V was discussed.In the past few years, it has been reported that 1,4-benzodiazepines undergo rearrangements leading to isoindoles,1,3) indoles,4) quinazolines,5-7) quinoxalines8) and quinolines.9)In the preceding paper, we have reported1 on the base-catalyzed intramolecular rearrangements of benzo [6,7]-1,4-diazepino [5,4-b] oxazoles giving isoindole and acridanone derivatives, and on the reactions of I with N,N-dimethyl formamide (DMF) in the presence of sodium hydride affording exo-methylene compounds as shown in Chart 1. Our interest in the for-

Regioselective Ring Expansion of Isatins with In Situ Generated α-Aryldiazomethanes: Direct Access to Viridicatin Alkaloids

“…Consequently, various synthetically feasible protocols have evolved for the construction of these important and attractive scaffolds. − Traditional strategies for the synthesis of 4-arylquinolin-2­(1 H )-ones include ring expansion of isatins with either diazomethanes/EDA under the catalysis of NHC-dirhodium­(II)/TMS-diazomethane in the presence of TFA, followed by C-4 arylation using conventional coupling reactions. They can also be synthesized by (i) Diels–Reese reaction, (ii) Knoevenagel condensation/epoxidation, followed by decyanative epoxide-arene cyclization of cyanoacetanilides, (iii) decarboxylative rearrangement of cyclopenin and cyclopenol, and (iv) PhI­(OCOCF 3 ) 2 -mediated α-hydroxylation, followed by acid-promoted intramolecular annulation of N -phenylacetoacetamide (Scheme ). …”

Synthesis and Mechanistic Insights of the Formation of 3-Hydroxyquinolin-2-ones including Viridicatin from 2-Chloro-N,3-diaryloxirane-2-carboxamides under Acid-Catalyzed Rearrangements

“…Considering the broad interest in 4-aryl-2-quinolinones, various methods for their synthesis have been reported. − Traditional strategies for the synthesis of 4-arylquinolin-2­(1 H )-ones include ring expansion of isatins with either diazomethanes/EDA under the catalysis of NHC dirhodium­(II), developed by Candeias and Gois et al or TMS-diazomethane in the presence of trifluoroacetic acid (TFA), developed by Arnold and LaVoie et al followed by C-4 arylation of quinolin-2­(1 H )-one via its 4-bromo derivative using conventional coupling reactions (Scheme a). Quinolin-2­(1 H )-ones for arylation can also be synthesized via the Diels–Reese reaction .…”

“…Quinolin-2­(1 H )-ones for arylation can also be synthesized via the Diels–Reese reaction . There are also exclusive methods for the synthesis of 4-arylquinolin-2­(1 H )-ones, for example, decarboxylative rearrangement of cyclopenin and cyclopenol, described by the White and Smith groups (Scheme b) and by the Tachikawa group (Scheme c) . Kobayashi and Harayama reported an efficient method for the synthesis of 4-arylquinolin-2­(1 H )-ones involving Knoevenagel condensation/epoxidation, followed by decyanative epoxide-arene cyclization of cyanoacetanilides (Scheme d) and later PhI­(OCOCF 3 ) 2 -mediated α-hydroxylation, followed by acid-promoted intramolecular annulation of N -phenylacetoacetamide was demonstrated for the synthesis of 4-arylquinolin-2­(1 H )-ones by Du and Zhao (Scheme e) .…”

“…16 There are also exclusive methods for the synthesis of 4-arylquinolin-2(1H)-ones, for example, decarboxylative rearrangement of cyclopenin and cyclopenol, described by the White and Smith groups (Scheme 1b) 17 and by the Tachikawa group (Scheme 1c). 18 Kobayashi and Harayama reported an efficient method for the synthesis of 4arylquinolin-2(1H)-ones involving Knoevenagel condensation/ epoxidation, followed by decyanative epoxide-arene cyclization of cyanoacetanilides (Scheme 1d) 19 and later PhI(OCOCF 3 ) 2mediated α-hydroxylation, followed by acid-promoted intramolecular annulation of N-phenylacetoacetamide was demonstrated for the synthesis of 4-arylquinolin-2(1H)-ones by Du and Zhao (Scheme 1e). 20 Klaśek et al reported the synthesis of 4-aryl-3-hydroxyquinolin-2(1H)-ones via the H 2 SO 4 -catalyzed pinacol rearrangement of cis- 3-aryl-3,4-dihydro-3,4dihydroxyquinolin-2(1H)-ones obtained from 3-aryl-3-hydroxyquinoline-2,4-diones by reduction with NaBH 4 (Scheme 1f).…”

Ring‐Expansion Reaction of Isatins with Ethyl Diazoacetate Catalyzed by Dirhodium(II)/DBU Metal‐Organic System: En Route to Viridicatin Alkaloids

“…Rather surprisingly, the synthesis of 3‐hydroxy‐4‐arylquinolin‐2(1 H )‐ones has been a relatively overlooked topic in the literature. Early methods described the synthesis of this family of compounds using the addition of aryldiazomethanes to isatins,14,15 treatment of cyclopenin with hydrochloric acid,16 ring contraction of benzodiazepinooxazoles17 or through the use of Friedländer‐type condensations 5b,7,8,18. In most cases, these approaches displayed a poor breadth of substrate compatibility and consequently were found not practical for preparation of 3‐hydroxy‐4‐arylquinolin‐2(1 H )‐ones derivative libraries for biological evaluation.…”