A general and efficient 2-amination of pyridines and quinolines

Pyridine N-oxides were converted to 2-aminopyridines in a one-pot fashion using Ts2O-t-BuNH2 followed by in situ deprotection with TFA. The amination proceeded in high yields, excellent 2-/4-selectivity, and with good functional group compatibility. 2-Amino (iso)quinolines were also obtained in the same manner. Combined with the simple oxidation of pyridines to pyridine N-oxides, this method provides a general and efficient way for amination of 2-unsubstituted pyridines.     

Synthesis of 1-[1-bromo-2-benzoyl(2-thenoyl)vinyl]-1,1-dimethylhydrazinium bromides from 1-bromo-2-benzoyl(2-thenoyl)acetylenes and 1,1-dimethylhydrazine

1-[1-Bromo-2-benzoyl(2-thenoyl)vinyl]-1,1-dimethylhydrazinium bromides were synthesized by the reactions of 1-aroyl-2-bromoacetylenes withN,N-dimethylhydrazine in acetonitrile at 20°C. The structure of 1-(2-benzoyl-1-bromovinyl)-1,1-dimethylhydrazinium bromide was established by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1536–1538, August, 1999.     

Selective conversion of diallylanilines and arylimines to quinolines

A variety of diallylanilines are shown to undergo cobalt-carbonyl catalyzed rearrangement to quinolines. Diallylanilines are also used as allyl transfer reagents to convert benzaldimines into quinolines. Substitution in the 2- and 3-positions of the quinoline is featured in all transformations.     

Synthesis of benzazepines and their rearrangement to quinolines and pyrrolo(2,3-b) quinolines

BECKMANN or SCHMIDT rearrangement of ethyl trans-4-oxo-1-phenyl-2-tetralincarboxylate ( 2 ) affords ethyl trans-2,3,4,5-tetrahydro-2-oxo-5-phenyl-1H-benzo [b] azepine-4-carboxylate ( 4 ). Mild treatment of trans-2,3,4,5-tetrahydro-1-methyl-2-oxo-5-phenyl-1 H-benzo-[b] azepine-4-carboxylic acid ( 7 ) with thionyl chloride and pyridine in dimethylformamide and subsequent reaction with an amine yields the corresponding benzazepine-4-carboxamide. If he it is applied during the preparation of the acid chloride, rearrangement occurs yielding cis and trans derivatives of hydrocarbostyril. 2,3,4,5-Tetrahydro-1,4-methano-1-methyl-5-phenyl-1 H-benzo-[b] azepinium chloride ( 25 ) reacts with primary or secondary amines to cis-tetrahydroquinoline derivatives. When heated above its melting point, trans-4,5-dihydro-2-methylamino-5-phenyl-3H-benzo-[b] azepine-4-carboxylic acid ( 29 ) rearranges with elimination of water to a mixture of cis-and trans-2,3,3a,4-tetrahydro-1-methyl-2-oxo-4-phenyl-1H-pyrrolo [2,3-b] quinoline ( 32 and 31 ). The reduction of 31 was investigated. The mechanisms of the rearrangements are discussed.     

Palladium-catalyzed approach for the general synthesis of (E)-2-arylmethylidene-N-tosylindolines and (E)-2-arylmethylidene-N-tosyl/nosyltetrahydroquinolines: access to 2-substituted indoles and quinolines

A facile and efficient method for the synthesis of (E)-2-arylmethylidene-N-tosylindolines and (E)-2-arylmethylidene-N-tosyl/nosyltetrahydroquinoline variants has been developed through palladium-catalyzed cyclocondensation of aryl iodides with readily available 1-(2-tosylaminophenyl)prop-2-yn-1-ols and their higher homologues, respectively. The proposed reaction mechanism invokes the operation of trans-aminopalladation during cyclization (5/6-exo-dig), which ensures exclusive (E)-stereochemistry in the products. The method is fast, operationally simple, totally regio- and stereoselective, and versatile enough to access a variety of 2-substituted indoles and quinolines. The reactions proceeded efficiently with a wide variety of substrates and afforded the corresponding products in moderate to excellent yields.     

A new access to substituted tetraethyl N-Boc 2-aminoethylidene-1,1-bisphosphonates and phosphonyl-substituted aza-Morita-Baylis-Hillman-type adducts

A general one-pot synthesis of substituted 2-aminoethylidene-1,1-bisphosphonates has been developed. The protocol involves base-induced addition of sodium tetraethyl methylenebisphosphonate to N-Boc imines generated in situ from N-Boc-α-amidoalkyl-p-tolylsulfones by the action of sodium hydride. The direct and efficient conversion of the title compounds into aza-Morita-Baylis-Hillman-type adducts has been also elaborated.     

Synthesis of imidazolidin-4-ones and their conversion into 1,4-benzodiazepin-2-ones

α-Haloacetanilides Ia-e react with hexamine in ethanol giving the bisimidazolidin-4-one derivatives IIa-e, which hydrolize, in acidic media into the corresponding mono-imidazolidin-4-ones IIIa-e. The compounds IIa-d were converted into 1,4-benzodiazepin-2-ones, under different conditions and in the presence of a variety of agents. The yields were between 50 and 100%.     

A straightforward and general access to α-phthalimido-α′-substituted propan-2-ones

The regioselective ring opening of the commercially available N-(2,3-epoxypropyl)phthalimide with different nucleophiles, to obtain the corresponding phthalimidopropan-2-ols (including a challenging fluorohydrin) followed by the Dess-Martin periodinane oxidation, constitutes a general and widely applicable protocol for the preparation of differently functionalized α-phthalimido-α′-substituted propan-2-ones. The incorporation of the substituent in the α′ position takes place in an early stage of the process, thus furnishing a divergent and valuable approach.     

A general,enantioselective synthesis of 2-substituted thiomorpholines and thiomorpholine 1,1-dioxides

In the course of our drug discovery programs, we had need to access chiral, 2-substituted thiomorpholines and their oxidized congeners, thiomorpholine 1,1-dioxides. Here, we disclose a high-yielding, general protocol for the enantioselective synthesis of C2-functionalized thiomorpholines and thiomorpholine 1,1-dioxides.     

A novel synthesis of 2-arylhydrazono-6-amino-4-arylbenzene-1,3-dicarbonitriles and their conversion into phthalazines

Compounds 1a-d react with benzylidenemalononitrile 2 to yield dihydroaminopyridazines 3a-d and, in contrast, compounds 1e,f react with 2 under the same conditions to yield aminobenzenedicarbonitriles 8e,f compound 8e underwent intramolecular cyclization to phthalazine 9e. Compound 10e reacted with 2a to yield 11e.     

A general approach to access 5,6-dihydroindolo-naphthyridine ring system

We report a general approach for the synthesis of 5,6-dihydroindolo-naphthyridine ring system via an intramolecular cyclization of the indole NH to an alkene moiety as the key step.     

The simplest phenylnitrones and their conversion into isoxazolidine derivatives

Reactions of N-phenylhydroxylamine with the simplest alkanals leads initially to the formation of N-phenylnitrones, dimerization of which gives 5-substituted isoxazolidine. Taking the reactions of N-phenylnitrones, benzaldehyde, and acetone as an example, the possibility of a crossover reaction has been established.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 838–841, June, 1988.     

One-pot conversion of 1,1-dibromoalkenes into internal alkynes by sequential Suzuki-Miyaura and dehydrobromination reactions

A protocol for the one-pot synthesis of internal alkynes from 1,1-dibromoalkenes is reported. The method is hinged upon the Suzuki-Miyaura cross-coupling of 2-aryl- or 2-heteroaryl-1,1-dibromoalkenes with aryl or heteroaryl boronic acids or borate esters followed by dehydrobromination of the intermediate coupled products. Yields up to 89% were obtained.     

Synthesis of alpha-CF2-mannosides and their conversion to fluorinated pseudoglycopeptides

A methodology allowing the synthesis alpha-CF(2)-mannosides, based on the addition of a difluoroenoxysilane to a glycal followed by a dihydroxylation reaction, is described. The resulting 2,2-difluoro-2-mannosylacetate is converted into two pseudoglycopeptides which may act as E- and P-selectin inhibitors.     

A new access to 2-phosphonothiophenes

2-Phosphonothiophenes are prepared via the reaction of β-chloroacroleins with diethyl mercaptomethylphosphonate.     

A facile access to 2-deoxy-l-ribose

The title compound was prepared in five steps starting from R-(+)-5-benzyloxymethyl-5H-furan-2-one 1 via syn-dihydroxylation of its double bond, regioselective tosylation of the 2-OH group in the thus obtained diol 2 followed by selective deoxygenation of that position.     

A mild conversion of arylboronic acids and their pinacolyl boronate esters into phenols using hydroxylamine

Hydroxylamine was found to be a mild reagent for conversion of arylboronic acids and their pinacolyl boronate esters into phenols. This procedure works on most arylboronic acids at room temperature, yielding phenols in moderate to good yields, and efficiently on arylboronates also yielding phenols in good yields.     

Pyrazolobenzothiazoles and their conversion to cyanine dyes

Thiocyanatlon of 5- and 6-aminoindazoles gives 5-amino-4-thiocyanoindazole and 6-amino-7-thiocyanoindazole. Sodium sulfide reduction of these amlnothiocyano derivatives, followed by cyclization with acetic anhydride gives 2-methylpyrazolo[5, 4-g] benzothiazole and 2-methylpyrazolo[4, 5-g]benzothiazole. Dimethyl sulfate alkylation in alkaline solution gives 2, 6-dimethylpyrazolo[5, 4-g]benzothiazole and 2, 8-dimethylpyrazolo[4, 5-g]benzothiazole. Quaternary salts of the latter were used to synthesize symmetrical and unsymmetrical trimethinecyanines, monomethinecyanines, and dimethinemerocyanines containing the thiocyano group, as well as styryl dyes. It is found that 2-methylpyrazolo[4, 5-g]benzothiazole is less basic than 2-methylpyrazolo[5,4-g]benzothiazole and more basic than unsubstituted benzothiazole.     

A two-step approach to 2-polyfluoroalkyl quinolines from N-aryl polyfluoroalkyl imidoyl iodides

2-Polyfluoroalkyl quinoline derivatives were synthesized from the enaminones which were obtained from the reaction of N-aryl polyfluoroalkyl imidoyl iodides with methyl ketones.