ChemInform Abstract: A Straightforward Synthesis of Pyridopyrazino[2,3-b]indoles and Indolo[2,3-b]quinoxaline (original) (raw)
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ChemInform, 2015
Halogen compounds P 0030 A Straightforward Synthesis of Alkenyl Nonaflates from Carbonyl Compounds Using Nonafluorobutane-1-sulfonyl Fluoride in Combination with Phosphazene Bases.-A general chemo-and regioselective synthesis of alkenyl nonaflates uses purified fluoride (II) and a phosphazene base. The regioselectivity of the process [e.g. for (VIII)] can be significantly influenced by the type of phosphazene base.-(VOGEL,
Tetrahedron, 1990
We now report a fundamentally new simple and apparently general method to the synthesis of fused pyrroles, namely, pyrrolo [ 1,2-alquinoxalines, indolo[3,2c]quinolines and indolo [ 1,2-c]quinazolines. Our approach is centered on the aza-Wittig type reaction of iminophosphoranes with heterocumulenes: e.g. isocyanates, isothiocyanates, carbon dioxide and carbon disulfide to give o-pyrrolylphenyl heterocumulenes 1, which subsequently undergo ring closure leading to the fused pyrroles 2 (Chart 1).
Tetrahedron, 1999
Cyclic and acyclic ~-ketoesters 4, a typical cyclic ct-diketone 5 and a typical cyclic [~-diketone 6 were converted to the corresponding vinyl nonaflates of general formula 7, 8 and 9, respectively, by reaction with 1.2-1.5 equiv of Nail in DMF at 20-55 °C followed by treatment with 1.15-1.30 equiv of perfluoro-l-butanesulfonyl fluoride at 20 °C. These vinyl nonaflates, which were purified by MPLC on silica gel, proved to be excellent electrophiles in Pal-catalyzed cross-coupling reactions with aryl-, l-alkynyl-and alkylzinc chlorides. A variety of cyclic and acyclic tetrasubstituted c~,l~-unsaturated esters which included stereoisomerically pure compounds, a 2substituted 3-aryi-2-cyclopentenone and naturally-occurring dihydrojasmone were cleanly synthesized by these smooth and selective cross-coupling reactions.
ChemInform Abstract: Convenient One-Pot Synthesis of N-Substituted 3-Trifluoroacetyl Pyrroles
Cheminform, 2009
Preparation of 2-oxazoline, a versatile intermediate in synthetic chemistry, from carboxylic acids is a classical and useful method. Since 2-oxazolines can be readily re-converted into carboxylic acids, they can be used as a protecting group for carboxylic acids. 3,6) Among various methods employed to convert derivatives of carboxylic acids to the oxazolines, intramolecular dehydrohalogenation of N-(bhaloethyl)amides to give 2-oxazolines is well established. Although the reaction readily takes place by treatment with either base or silver ion, such reactions have not adapted well to the preparation of 2-oxazolines, presumably because of the cumbersome method used to prepare N-(b-haloethyl)amides. For example, they have been prepared by Ritter reaction of nitriles with halohydrins or haloalkenes, 8) chlorination of N-(b-hydroxyethyl)amides with thionyl chloride, 9) and coupling of 2-haloethylammonium salts with acid chlorides 10,11) or acid anhydrides. We report here a simple and general one-pot method to prepare 2-oxazolines from carboxylic acids; the reaction involves dehydrocondensation of carboxylic acids and 2haloethylammonium salts leading to the formation of N-(bhaloethyl)amides, which then can be readily converted into 2-oxazolines by base treatment.
Regiospecific one-pot synthesis of new trifluoromethyl substituted heteroaryl pyrazolyl ketones
Journal of Heterocyclic Chemistry, 2005
A convenient and general method for the regiospecific synthesis of three novel series of 1-(2-thenoyl)-, 1-(2furoyl)-and 1-(isonicotinoyl)-3-alkyl(aryl)-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-pyrazoles, in good yields (53-91 %), from the cyclocondensation reactions of 1,1,1-trifluoro-4-alkoxy-4-alkyl(aryl)-but-3-en-2ones, where alkyl = H and Me; aryl =-C 6 H 5 , 4-CH 3 C 6 H 4 , 4-CH 3 OC 6 H 4 , 4-FC 6 H 4 , 4-ClC 6 H 4 , 4-BrC 6 H 4 , 4-NO 2 C 6 H 4 with 2-thiophenecarboxylic hydrazide, furoic hydrazide and isonicotinic acid hydrazide, respectively, is reported. Subsequently dehydration reaction of phenyl substituted 2-pyrazolines with P 2 O 5 furnished the corresponding 1H-pyrazoles as mixture of regioisomers and in low yields (35-36 %).
Organic Letters, 2002
6-Trifluoromethyl-12-acylindolo[1,2-c]quinazolines are prepared in high yield through the palladium-catalyzed reaction of bis(o-trifluoroacetamidophenyl)acetylene with aryl or vinyl halides and triflates. The reaction, which tolerates a variety of important functional groups, probably involves the formation of a 3-acyl-2-(o-trifluoroacetamidophenyl)indole intermediate, followed by its cyclization to the indoloquinazoline product. We have recently reported that o-(o-aminophenylethynyl)trifluoroacetanilide 1 reacts with aryl iodides in the presence of carbon monoxide to give 2-(o-trifluoroacetamidophenyl)-3-acylindole 3 derivatives that, in turn, cyclize to indolo-[3,2-c]quinolines 4 1 (Scheme 1). During this study, formation of 6-trifluoromethyl-12-acylindolo[1,2-c]quinazolines 2,3 as byproducts was observed in some cases. For example, the reaction of 1 with m-trifluoromethylphenyl iodide under our standard conditions [Pd(PPh 3) 4 , K 2 CO 3 , MeCN, 50°C] afforded the expected 3-acylindole derivative 3a in 66% yield along with a 17% yield of the indoloquinazoline product 5a (Scheme 2). The presence of the indolo[1,2-c]quinazoline skeleton in natural substances such as Hinckdentine A, 4 an unusual marine alkaloid that has been isolated from the bryozoan
Org. Biomol. Chem., 2013
Melting points are uncorrected. All of the reagents, catalysts, and solvents are commercially available and were used as purchased, without further purification. The appropriate 2alkynyltrifluoroacetanilides were prepared, usually in high yields, from 2-iodoaniline via a two-step process involving a Sonogashira cross-coupling with terminal alkynes followed by a trifluoracetylation step. 1 Reaction products were purified on axially compressed columns, packed with SiO2 25-40 μm, connected to a preparative pump for solvent delivery and to a refractive index detector, and eluting with n-hexane/EtOAc mixtures. 1 H NMR (400.13. MHz), 13 CNMR (100.6 MHz) and 19 F NMR (376.5 MHz) spectra were recorded with a Bruker Avance 400 spectrometer. Splitting patterns are designed as s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet), or bs (broad singlet). IR spectra were recorded with a Jasco FT/IR-430 spectrometer. Mass spectra were determined with a QP2010 Gas Chromatograph Mass spectrometer (EI ion source). General Procedure. Preparation of 2-phenyl-3-(4-methoxyphenyl)indole 3a In a 50 mL Carousel Tube Reactor (Radely Discovery Technology) containing a magnetic stirring bar Pd(OAc) 2 (3.8 mg, 0.0172 mmol) and dppp (7.1 mg, 0.0172 mmol) were dissolved at room temperature with 1.0 mL of anhydrous MeOH. Then, o-(phenylethynyl)trifluoroacetanilide (100.0 mg, 0.345 mmol), 4-methoxyphenylboronic acid (105.0 mg, 0.690 mmol), K 3 PO 4 (146.7 mg, 0.690 mmol), and 1.0 mL of solvent were added. The mixture was stirred for 1.5 h at 60 °C under a balloon of molecular oxygen. After this time, the reaction mixture was cooled to room temperature, diluted with EtOAc, and washed with water. The organic extract was dried over Na 2 SO 4 and concentrated under reduced pressure. The residue was purified by chromatography (silica gel, nhexane/EtOAc 85/15 v/v) to afford 78.4 mg (76% yield) of 3-(4-methoxyphenyl)-2-phenyl-1Hindole: mp: