Synthesis of chalcogeno lactones. II. 3, 4-dihydro-1 H-2-benzothiin-3-one, 3,4-dihydro-1H-2-benzoselenin-3-one and 3,4-dihydro-1H-2-benzotellurin-3-one

The synthesis of 3, 4-dihydro-1H-benzothiin-3-one and its selenium and tellurium analogs is reported from o-bromomethylphenylacetyl chloride and sodium hydrogen chalcogenates, via phase-transfer catalysis.     

Design and synthesis of novel tricycles based on 4H-benzo[1,4]thiazin-3-one and 1,1-dioxo-1,4-dihydro-2H-1lambda6-benzo[1,4]thiazin-3-one

This paper reports our recent efforts to develop novel tricycles based on 4H-benzo[1,4]thiazin-3-one ( 2) and 1,1-dioxo-1,4-dihydro-2H-1lambda(6)-benzo[1,4]thiazin-3-one (3) using 1,5-difluoro-2,4-dinitrobenzene (1). All of these tricycles integrate two privileged structures into one skeleton, including 3,8-dihydro-5-thia-1,3,8-triaza-cyclopenta[b]naphthalene-7-one (4, 10, 12), 5,5-dioxo-3,5,6,8-tetrahydro-5lambda(6)-thia-1,3,8-triaza-cyclopenta[b]naphthalene-7-one (5, 11), 3,8-dihydro-5-thia-1,2,3,8-tetraaza-cyclopenta[b]naphthalene-7-one (6), 5,5-dioxo-3,5,6,8-tetrahydro-5lambda(6)-thia-1,2,3,8-tetraaza-cyclopenta[b]naphthalene-7-one (7), 3,8-dihydro-1H-5-thia-1,3,8-triaza-cyclopenta[b]naphthalene-2,7-dione (8), and 5,5-dioxo-3,5,6,8-tetrahydro-1H-5lambda(6)-thia-1,3,8-triaza-cyclopenta[b]naphthalene-2,7-dione (9). A typical library of scaffold 5 was synthesized in a parallel solution-phase manner and analyzed by HPLC-UV-MS or HPLC-UV-ELSD method.     

Synthesis of 4,5-dihydro-1H,3H-thieno[3,4-c]thiophene and 4,5-dihydro-1H,3H-thieno[3,4-c]furan

4,5-Dihydro-1H,3H-thieno[3,4-c]thiophene and 4,5-dihydro-1H,3H-thieno[3,4-c]furan were synthesized by retro Diels-Alder reactions under flash vacuum thermolysis conditions.     

Reactions of anthranilamide with isocyanates: A new facile synthesis of 2,3-dihydro-5H-oxazolo[2,3-b]quinazolin-5-one and 3,4-dihydro-2H,6H-[1,3]oxazino[2,3-b]quinazolin-6-one [1]

2,3-Dihydro-5H-oxazolo[2,3-b]quinazolin-5-one 5a was synthesized from anthranilamide 1 and 2-chloro-ethyl isocyanate either by a direct reflux in methanol, or by stirring at room temperature in acetonitrile leading to the intermediate, 2-(2-chloroethyl ureido)benzamide 6a which was subsequently cyclized on heating with an organic base. However, when compound 6a was refluxed with concentrated hydrochloric acid, it furnished 3-(2-chloroethyl)-2,4-dioxo-1H,3H-quinazoline 2a in good yields. 3,4-Dihydro-2H,6.H-[1,3]-oxazino[2,3-b]quinazolin-6-one 5b , 3-(3-chloropropyl)-2,4-dioxo-1H,3.H-quinazoline 2b and 2-(3-chloropropyl ureido)benzamide 6b were obtained similarly from 1 and 3-chloropropyl isocyanate.     

New method for the synthesis of 4-aryl-3,4-dihydro-2H-benzo[g]chromene-2,5,10-triones

Abstract

We report herein a new method for the synthesis of 4-aryl-3,4-dihydro-2H-benzo[g]chromene-2,5,10-triones 4 that proceeds in good yields (74–86%) and mild reaction conditions between readily available 2-amino-4-aryl-5,10-dioxo-5,10-dihydro-4H-benzo[g]chromene-3-carbonitriles 1, and formic acid (88%), at reflux for 6?h. In addition, we have also studied the antioxidant activities using DPPH and total TAC methods.     

Parallel solution-phase synthesis of 4H-benzo[1,4]thiazin-3-one and 1,1-dioxo-1,4-dihydro-2H-1lambda6-benzo[1,4]thiazin-3-one derivatives from 1,5-difluoro-2,4-dinitrobenzene

This paper discusses the synthesis of privileged structures 4H-benzo[1,4]thiazin-3-one and 1,1-dioxo-1,4-dihydro-2H-1lambda6-benzo[1,4]thiazin-3-one derivatives in a parallel solution-phase manner using 1,5-difluoro-2,4-dinitrobenzene. Each scaffold possesses four diversity points. A cheap and efficient oxidant, urea-hydrogen peroxide (UHP), was applied for the introduction of the sulfone group. The intramolecular cyclization to 1,1-dioxo-1,4-dihydro-2H-1lambda6-benzo[1,4]thiazin-3-one was achieved by microwave assistance or the use of an inorganic base.     

Novel synthesis of spirocyclic-3,4-dihydro-2H-benzo[b][1,4]oxazine derivatives

A two-step procedure involving acid catalyzed ring opening of spirocyclic epoxides with 2-haloanilines and subsequent palladium-catalyzed intramolecular C–O bond formation to provide spirocyclic-3,4-dihydro-2H-benzo[b][1,4]oxazine derivatives is described.     

Derivatives of 3,4-dihydro-2H-benzo[b][1,4]dioxepin. Preparation of 7,8-dihydro-6H-[1,4]dioxepino[2,3-f]-2,1,3-benzoxadiazole 1-oxide

A novel annelated benzofuroxan 4 and a benzofurazan 4a have been prepared in good yields. Nitration of 5 afforded both trinitro derivatives 6 and 7 . Low temperature nmr spectroscopy was applied on compound 4 and the value ΔG* is reported.     

The enantioselective synthesis of (R)- and (S)-3-amino-3,4-dihydro-1H-[1,8]naphthyridin-2-one

A number of approaches to the enantioselective synthesis of (R)- and (S)-3-amino-3,4-dihydro-1H-[1,8]naphthyridin-2-one were studied. A novel one-pot asymmetric reduction/lactamization provided the desired products in high yield and enantiomeric excess.     

Unambiguously confirmed structure of 2-phenacylidene-1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one and 3-phenacylidene-3,4-dihydro-1H-pyrido[2,3-b]pyrazin-2-one

To determine the structures of two isomeric products, 2-phenacylidene-1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one (2) and 3-phenacylidene-3,4-dihydro-1H-pyrido[2,3-b]pyrazin-2-one (3) obtained by condensation of 2,3-diaminopyridine (1) with ethyl benzoylpyruvate [1–3], these compounds were hydrolyzed to give 2-methyl-4H-pyrido[2,3-b]pyrazin-3-one (4) and 3-methyl-1H-pyrido[2,3-b]pyrazin-2-one (5) , respectively [4,5]. Both hydrolysates 4 and 5 were hydrogenated to afford 2-methyl-1,2-dihydro-4H-pyrido[2,3-b]pyrazin-3-one (6) and 3-methyl-3,4-dihydro-1H-pyrido[2,3-b]pyrazin-2-one (7) . The latter compound was identical with an unequivocally synthesized compound providing proof for the structures of all these compounds.     

New synthesis of 3-amino-1H-benzo[f]chromene-2-carbonitriles

3-Amino-1H-benzo[f]chromene-2-carbonitriles were synthesized by non-catalytic reaction from Mannich bases of the naphthalene series and malononitrile. Reactive 1-benzylidene(or methylidene)naphthalen-2(1H)-ones were presumed as intermediate products.     

Liquid-phase parallel synthesis of combinatorial libraries of substituted 6-carbamoyl-3,4-dihydro-2H-benzo[1,4]thiazines

In this work, we explored several original combinatorial derivatization patterns for the 3,4-dihydro-2H-1,4-benzothiazine scaffold. The synthesis begins with commercially available 4-chloro- and 4-fluoro-3-nitrobenzoates and employs a sequence of moderate and high-yielding reactions that display a relatively high substituent tolerance. Simple manual techniques for parallel reactions were coupled with easy workup and purification procedures to give high-purity final products. The developed approach was easily adaptable for parallel synthesis of more than 2600 novel 2H-benzo[1,4]thiazine-6-carboxylic acid amides, which were efficiently prepared in a semiautomatic fashion using special CombiSyn synthesizers.     

Preparation and alkylation of 1,5-dihydro-3H-1,2,4-thiadiazolo[3,4-b]quinazolin-5-one 2,2-dioxides

1,5-Dihydro-3H-1,2,4-thiadiazolo[3,4-b]quinazolin-5-one 2,2-dioxides ( 3 ) are prepared by reaction of isatoic anhydrides with methyl N-(chloromethanesulfonyl)carbamimidothioate ( 6 ). The sodium salt of 3a , generated with sodium hydride in N,N-dimethylformamide, is alkylated excusively on N-10. An improved preparation of 6 is described, utilizing a two-phase sulfonylation.     

Synthesis of phenyl-substituted 2H-3,4-dihydro-3-aminomethyl-1,4-benzoxazines. Intermediates for 1H-2,3,3a,4-tetrahydroimidazo[5,1-c][1,4]benzoxazin-1-one derivatives. Part II

The synthesis of 2H-3, 4-dihydro-3-aminomethyl-1, 4-benzoxazines substituted by one phenyl group in the 2, 3 or α-position is reported. The two diastereoisomers of the 2-phenyl-derivative were independently synthesized from ethyl trans-3-phenylglycidate by a stereospecific route. A previous attempt at the synthesis of these same compounds gave rise to an unexpected aliphatic-aromatic ketone rearrangement.     

A convenient synthesis of 3,4-dihydro-2-methyl-3-oxo-2H-1,4-benzoxazine-2-carboxylic acids and 3,4-dihydro-2-methyl-3-oxo-2H-pyrido[3,2-b]-1, 4-oxazine-2-carboxylic acid

A convenient one pot synthesis of ethyl 3,4-dihydro-2-methyl-3-oxo-2H-1,4-benzoxazine-2-carboxylates and 3,4-dihydro-2-methyl-3-oxo-2H-pyrido[3,2-b]-1,4-oxazine-2-carboxylates and their conversion into the respective carboxylic acids are described.     

Synthesis and Anticonvulsant Activity of 9-Alkoxy-6,7-dihydro-2H-benzo[c][1,2,4]triazolo[4,3-a]azepin-3[5H]-ones

A series of novel 9-alkoxy-6,7-dihydro-2H-benzo[c][1,2,4]triazolo[4,3-a]azepin-3(5H)-one derivatives was designed and synthesized starting from 2,3,4,5-tetrahydro-7-hydroxy-1H-2-benzazepin-1-one. The structures of these compounds were confirmed by mass, ¹H NMR infrared spectra, and elemental analysis. Their anticonvulsant activity was evaluated by maximal electroshock (MES) test, and their neurotoxic effects were determined by the rotarod neurotoxicity test. The results shown that 3k was the most active compound with median effective dose (ED₅₀) of 27.3 mg/kg, median toxicity dose (TD₅₀) of 118.3 mg/kg, and protective index (PI) of 4.3. Possible structure–activity relationship is discussed.     

A new one-step synthesis of 2,3-dihydro-5H-thiazolo[2,3-b]quinazolin-5-one and 3,4-dihydro-2h,6h[1,3]thiazino[2,3-b] quinazolin-6-one

2,3-Dihydro-5H-thiazolo[2,3-b]quinazolin-5-one and 3,4-dihydro-2H,6H[1,3] thiazino[2,3-b]-quinazolin-6-one have been synthesized in one step by the reaction of methyl anthranilate with ehloroalkyl isothiocyanates.