Mechanisms of cyclisation of indolo oxime ethers I. Formation of ethyl 9,11-dimethoxy indolo[2,3-c]quinoline-6-carboxylates

Oxime ethers as versatile precursors in organic synthesis: a review

“…It should be noted that the presence of an electron donating substituent (R) at 4 00 position increases the rate of cyclization due to stabilization of the resonance. 67,68 This protocol also has been used by the same group for the generation of indazoles 54 and indoles 55 (Scheme 24). 69,70 Pyrroles are important building blocks for a number of biologically and pharmaceutically active compounds.…”

Review of the synthesis of acyclic and cyclic oxime ethers

“…The best-known method for synthesis of acyclic oxime ethers is the reaction of oximes with alkyl-and aryl halides (Scheme 1). [76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95] A safe method for the preparation of oximes involves reaction of carbonyl compounds (aldehydes and ketones) with hydroxyl amines (Scheme 2). [96][97][98][99][100][101] This type of reaction was introduced by Schiff 102 in 1864 and nowadays is the best choice for the synthesis of titled compounds.…”

“…87,93,94 As well as, the system Na/ alcohol has also been utilized. 78,85,88 Using potassium carbonate as base and acetonitrile as solvent clearly accelerated the alkylation of the oxime moiety compared to other bases/ solvents, and the desired products were synthesized in good yields (Table 1). 93 Recently, an excellent method for generation of oxime ethers 10a,b from oximes 9a,b and epichlorohydrin have been reported by Cerra and co-workers using acetone/water/K 2 CO 3 system (Scheme 3).…”

Pd(0)-Catalyzed Intramolecular Heck reaction of 2/3-Aryl(amino)methyl-3/2-bromoindoles: Syntheses of 3,4-Benzo[c]-β-carbolines, Benzo[4,5]isothiazolo[2,3-a]indole 5,5-Dioxides, and 1,2-Benzo[a]-γ-carbolines

“…13 C{ 1 H} NMR (75 MHz, CDCl 3 ): δ 145. 4, 138.9, 137.9, 137.4, 135.6, 134.7, 134.2, 131.1, 129.5, 129.3, 129.1, 128.8, 128.4, 126.7, 126.6, 124.5, 124.4, 124.0, 115.0, 36.8 2-Bromo-3-(bromomethyl)-1-(phenylsulfonyl)-1H-indole (8). To a solution of 2-bromo-3-methylindole (1 g, 2.86 mmol) in CCl 4 (30 mL), NBS (0.66 g, 3.72 mmol), and AIBN (0.1 g, 0.28 mmol) were added and refluxed for 1 h. After completion of the reaction (monitored by TLC), the floated succinimide was filtered off and filtrate was concentrated under reduced pressure.…”

“…Some of the recently reported methodologies to access β-carbolines (Figure ) involve Pd-catalyzed coupling of 3-iodo-2-iminoindole with substituted acetylene derivatives followed by cyclization, Bu 3 SnH-mediated radical cyclization of 3-bromo-2-aryl-( N -tosylamino)­methylindole, and regioselective Buchwald–Hartwig amination followed by Heck-type intramolecular arylation of 3-(2-bromophenylamino)­quinolines, electrocyclization of imino ether precursors, Pd(0)-catalyzed coupling of indole with 1-iodo-2-nitrobenzene followed by reductive cyclization, Pd­(II)-catalyzed coupling of 2-iminoindole with acetylene derivatives followed by cyclization, Ullmann cross-coupling of 2-iodocyclohex-2-en-1-ones with 3-nitro-4-iodopyrdine followed by Pd-catalyzed sequential reductive cyclization and dehydrogenation, and condensation of an in situ generated 1,5-diketone with ammonia . Apart from these reports, Mulcahy and co-workers outlined the synthesis of pyrido­[3,4- b ]­indoles utilizing Rh­(I)-catalyzed cyclization methodology .…”