Formation of Unsymmetrical 2-(Diacylmethylene)-2,3-dihydro-1H-benzimidazoles During Acidolysis of 1-Benzoyl-2-(β-benzoyloxy-β-phenylvinyl)-1H-benzimidazole

The reaction of 1-benzoyl-2-(-benzoyloxy--phenylvinyl)-1H-benzimidazole with carboxylic acids was investigated. A convenient method was developed for the synthesis of unsymmetrical 2-(diacylmethylene)-2,3-dihydro-1H-benzimidazoles. 2-(4-Pyrazolyl)-1H-benzimidazoles were obtained by the reaction of 2-(benzoylformylmethylene)-2,3-dihydro-1H-benzimidazole with hydrazine.     

Convenient syntheses of unsymmetrical imidazolidines

Unsymmetrical imidazolidines 10-14, optically active imidazolidines 20-22, and 2,3-dihydro-1H-benzimidazoles 28 and 29 were synthesized in good to excellent yields by Mannich reactions of 1,2-ethanediamines 8a-c, 18a-c, or N-methyl-1,2-benzenediamine (26a) with benzotriazole and formaldehyde, followed by the nucleophilic substitution of the benzotriazolyl group with C-nucleophiles (Grignard reagents, sodium cyanide), an S-nucleophile (benzenethiol), and a P-nucleophile (triethyl phosphite).     

Recyclization on interaction of arylhydrazones of 2-aroylmethyl-1H-benzimidazoles with ethyl isothiocyanate

Ethyl isothiocyanate reacts with arylhydrazones of 2-aroylmethyl-1H-benzimidazoles initiating recyclization with the formation of the previously unknown1-(1,3-diaryl-1H-pyrazol-5-yl)-1,3-dihydro-2H-benzimidazole-2-thiones. __________ Translated from Khimii Geterotsiklicheskikh Soedinenii, No. 4, pp. 522–527, April, 2006.     

Reaction of 2,3-Dihydro-1,5-benzothiazepines and Phenylacetyl Chloride in the Presence of Triethylamine： A New Aspect on the Formation Mechanism of Dihydro-1,3-oxazin-4-one Derivatives

2a,4-Disubstituted 2,2a,3,4-tetrahydro-2-phenyl-1H-azeto[2,1-d][ 1,5]benzothiazepin-1-ones, as well as 2-substi-tuted 2,3-dihydro-3-phenylacetyl-2-styryl-benzothiazoles and 4a,6-disubstituted 3- .benzyl-4a,5-d/hydro-2-phenyl-1H,6H-[1,3]oxazino[2,3-d][1,5]benzothiazepin-1-ones, were obtained from the reaction of 2,4-disubstituted 2,3-dihydro-1,5-benzothiazepines with phenylacetyl chloride in the presence of triethylamine. The mechanism for the formation of 4a,5-dihydro-1H,6H-[1,3]oxazino[2,3-d][1,5]benzothiazepin-1-ones, 2,3-dihydro-1,3-oxazin-4-one derivatives, was suggested.     

Synthesis of substituted 2,3-dihydro-1H-boroles by transmetalation of aluminacyclopent-2-enes with BF3·Et2O

A procedure was developed for selective synthesis of 4,5-dialkyl-1-fluoro-2,3-dihydro-1H-boroles via transmetalation of the corresponding aluminacyclopent-2-enes with BF₃·Et₂O. 4,5-Dialkyl-1-fluoro-2,3-dihydro-1H-boroles were isolated as complexes with BEtF₂. 4-Alkyl-5-dimethylaminomethyl-1-fluoro-2,3-dihydro-1H-boroles were synthesized for the first time.     

A novel reaction of (2a7-trinito-9H-fluoren-9-ylidene)-propanedinitrile with N-arylisoindolines

N-Arylisoindolines 1a-c reacted with (2,4, 7-trinitro-9H-fluoren-9-ylidene)propanedinitrile ( A ) in pyridine with admission of air via a net α-H-atom abstraction and formation of [3-(2-aryl-3-arylimino-2,3-dihydro- 1H-isoindol-1-ylidene)-2-aryl-2,3-dihydro-1H-isoindol-1-ylidene]propanedinitriles 2a-c , N-[2-aryl-3-(2-aryl-3-arylimino-2,3-dihydro-1H-isoindolyl-1-idene)-2,3-dihydro-1H-isoindol-1-ylidene]arenamines 3a, b , N, N'-[2-aryl-1H-isoindole-1,3(2H)-diylidene]bisarenamines 4a, b and N-arylphthalimides 5a-c in moderate yields. 2,4,7-Trinitro-9-fluorenone as well as one reduction product each of the latter and of A, namely compounds 6 and 7 , respectively, are also found. The structure of 2b has been unambiguously confirmed by an X-ray crystal structure analysis. A rationale for the conversions observed is presented. These involve dehydrogenation and oxidative couplings of 1a-c as well as transfer of N-aryl fragment from 1a-c to intermediate products.     

Stable carbenes. Synthesis and properties of benzimidazol-2-ylidenes

A new stable crystalline carbene, 1,3-bis(1-adamantyl)benzimidazol-2-ylidene, was synthesized by decomposition of 1,3-bis(1-adamantyl)-2,3-dihydro-1H-benzimidazol-2-ylacetonitrile on heating under reduced pressure. Heteroaromatic 1,3-R₂-disubstituted benzimidazol-2-ylidenes, both stable (R = 1-Ad) and generated in situ (R = Me, Bzl), as well as 1,3,4,5-tetraphenylimidazol-2-ylidene (generated in situ), reacted with acetonitrile to give the corresponding insertion products, 1,3-disubstituted 2-cyanomethyl-2,3-dihidro-1H-(benz)-imidazoles. The geometric parameters of 1,3-bis(1-adamantyl)benzimidazol-2-ylidene, determined by X-ray analysis, suggest its lower aromaticity as compared to imidazol-2-ylidenes and 1,2,4-triazol-5-ylidenes. The structures of 2-cyanomethyl-2,3-dihydro-1H-benzimidazoles, 2-cyanomethyl-1,3,4,5-tetraphenyl-2,3-dihydro-1H-imidazole, and 1-(1-adamantyl)-5-cyanomethyl-3,4-diphenyl-4,5-dihydro-1H-1,2,4-triazole are characterized by partial conjugation in the heteroring; some compounds exhibit luminescence under UV irradiation. 1,3-Bis(1-adamantyl)benzimidazol-2-ylidene reacted with molecular sulfur in benzene to give 1,3-bis-(1-adamantyl)-2,3-dihydro-1H-benzimidazole-2-thione, but it failed to react with selenium under analogous conditions.     

Synthesis of 2-substituted-5-halo-2,3-dihydro-4(H)-pyrimidin-4-ones and their derivatization utilizing the Sonogashira coupling reaction in the enantioselective synthesis of alpha-substituted beta-amino acids

A convenient, one-pot procedure for the synthesis of 1-benzoyl-2(S)-substituted-5-iodo-2,3-dihydro-4(H)-pyrimidin-4-ones by tandem decarboxylation/beta-iodination of the corresponding 6-carboxy-perhydropyrimidin-4-ones was developed. In addition, several 1-benzoyl-2(S)-substituted-5-bromo-2,3-dihydro-4(H)-pyrimidin-4-ones were readily prepared by bromination of 1-benzoyl-2(S)-substituted-2,3-dihydro-4(H)-pyrimidin-4-ones. Subsequently, Sonogashira coupling of the halogenated heterocyclic enones with various terminal alkynes produced 1-benzoyl-2(S)-isopropyl-5-alkynyl-2,3-dihydro-4(H)-pyrimidin-4-ones in good yields. Hydrogenation of the unsaturated C-C moieties in the Sonogashira products followed by acid hydrolysis afforded highly enantioenriched alpha-substituted beta-amino acids.     

Synthesis of halogen-substituted borolanes and 2,3-dihydro-1H-boroles by reactions of aluminacarbocycles with boron trichloride and boron tribromide

A selective procedure has been developed for the synthesis of 1-chloro(bromo)-substituted borolanes and 2,3-dihydro-1H-boroles by reaction of aluminacarbocycles with boron trihalides BX₃ (X = Cl, Br). 3-Substituted 1-chloro(bromo)borolanes and 2,3-dihydro-1H-boroles have been isolated as individual substances, and their structure has been determined.     

The <Emphasis Type="Italic">p</Emphasis>-(dimethylamino)benzaldehyde modification of Hantzsch reaction: Synthesis of 6-(1H-benzimidazol-2-yl)pyrido[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidino-2,4(1H, 3H)-diones

The reaction between p-(dimethylamino)benzaldehyde and 2-acylmethyl-1H-benzimidazoles and 6-amino-1,3-dimethylpyrimidino-2,4(1H,3H)-dione has given previously unknown 5-unsubstituted 6-(1H-benzimidazol-2-yl)pyrido[2,3-d]pyrimidino-2,4(1H,3H)-diones. The reaction occurs on boiling in acetic and acid and includes the formation of 1,4-dihydropyridine-bearing compounds in accordance with the Hantzsch reaction scheme and aromatization as a result of cleavage of N,N-dimethylaniline. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 585–589, April 2007.     

The mass spectral fragmentation of 1a,3-disubstituted 4-benzoyl-1a,2,3,4- tetrahydrooxazirino

The mass spectrometric behaviour of four 1a,3-disubstituted 4-benzoyl-1a,2,3,4-tetrahydrooxazirino[2,3-a][1,5]benzodiazepines has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and accurate mass measurements under electron impact ionization. All compounds show a tendency to eliminate a neutral oxygen atom, or oxygen atom plus benzoyl or aryl radicals, or oxygen atom plus CO molecule to yield 2,3-dihydro-1H-1,5-benzodiazepine derivative ions, or 1-benzoyl-2,3-dihydro-1H-1,5-benzodiazepine ions, which could further lose benzoyl to give 2,3-dihydro-1H-1,5-benzodiazepine ions. All compounds also show a tendency to eliminate a benzoyl radical to produce 1a,2,3,4-tetrahydrooxazirino[2,3-a][1,5]benzodiazepine ions. Both oxazirino[2,3-a][1,5]benzodiazepine ions and 2,3-dihydro-1H-1,5-benzodiazepine ions can undergo diazepine ring contraction rearrangement to yield benzimidazole ions by loss of propene or styrenes and other small fragments. The oxazirino[2,3-a][1,5]benzodiazepine ions [M(+)-PhCO] also undergo rearrangement reactions to form benzoxazole ions and benzimidazole ions. Copyright 1999 John Wiley & Sons, Ltd.     

Nitro derivatives of 1,3-dihydrobenzimidazol-2-one: I. Synthesis of <Emphasis Type="Italic">N</Emphasis>-nitrobenzimidazol-2-ones

1,3,5,6-Tetranitro-2,3-dihydro-1H-benzimidazol-2-one, 1,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-one, and 1,4,5,6-tetranitro-2,3-dihydro-1H-benzimidazol-2-one were synthesized for the first time by nitration of 5,6-di- and 4,5,6-trinitro-2,3-dihydro-1H-benzimidazol-2-ones with concentrated nitric acid in acetic anhydride.     

The condensation products of 6-methoxy-2,3-dihydro-4H-benzopyran-4-one and 6-nitroveratraldehyde. Part I

The condensation of 2,3-dihydro-6-methoxy-4H-benzopyran-4-one ( 1 ) and 6-nitroveratr-aldehyde ( 2 ) gave the expected 2,3-dihydro-6-methoxy-3-(6-nitroveratrylidene)-4H-benzopyran-4-one ( 3 ) plus an unexpected product identified as 2,3-dihydro-3-(α-ethoxy-4,5-dimethoxy-2-nitrobenzyl)-6-methoxy-4H-benzopyran-4-one ( 4 ).     

Minor withanolides from Physalis philadelphica: structures,quinone reductase induction activities,and liquid chromatography (LC)-MS-MS investigation as artifacts

As a result of a bioactivity-guided search for novel, plant-derived cancer chemopreventive agents, ixocarpalactone A (5) was isolated previously as a potent quinone reductase inducer from the leaves and stems of Physalis philadelphica. In the present study, this promising lead compound was reisolated in gram quantities for in vivo biological testing. During the course of this work, four additional minor new withanolides were also obtained and characterized, namely, 2,3-dihydro-3beta-methoxyixocarpalactone A (1), 2,3-dihydro-3beta-methoxyixocarpalactone B (2), 2,3-dihydroixocarpalactone B (3), and 4beta,7beta,20R-trihydroxy-1-oxowitha-2,5-dien-22,26-olide (4). However, compounds 1 and 2 were determined using liquid chromatography (LC)-MS-MS to be artifacts generated during the extraction and isolation procedure. Ixocarpalactone A was detected in the fresh fruits (tomatillos) of P. philadelphica by LC-MS-MS analysis at a concentration of 143+/-4.53 ppb.     

An efficient route to 6-(het)aryl-2-methyl-2,3-dihydro-1H-pyridin-4-ones as potential nAChRs ligands

A new efficient pathway to synthesise 6-(het)aryl-2-methyl-2,3-dihydro-1H-pyridin-4-ones is described. This reaction sequence involved, as a key step, a Suzuki cross-coupling reaction between various boronic acids and an 6-iodo-2,3-dihydropyridin-4-one. A final deprotecting step furnished the attempted products.     

丁酸氯维地平降解杂质的合成

以4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3,5-吡啶二羧酸(2-氰基乙基)（甲基）酯(5)为起始原料,合成了丁酸氯维地平的5种降解杂质：4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3,5-吡啶二羧酸单甲酯(A), 4-(2,3-二氯苯基)-1,4-二氢-2,6-二甲基-3-吡啶羧酸甲酯(B), 4-(2,3-二氯苯基)-2,6-二甲基-3,5-吡啶二羧酸单甲酯(C), 4-(2,3-二氯苯基)-2,6-二甲基-3,5-吡啶二羧酸（丁酰氧基甲基）（甲基）酯(D)和4-(2,3-二氯苯基)-2,6-二甲基-3-吡啶羧酸甲酯(E)。其中A由5水解制得;B由A脱羧制得;C由5氧化后再经水解制得;D由C和丁酸氯甲酯缩合制得;E由C脱羧制得,化合物结构经¹H NMR和MS（ESI）确证。     

A new base-induced ring transformation of pyrido[2,3-d]pyrimidines

8-Substituted 5,8-dihydro-5-oxopyrido[2,3-d]pyrimidine-6-carboxylates ( 3 ) rearranged to 8-substituted 7,8-dihydro-5-hydroxy-7-oxopyrido[2,3-d]pyrimidine-6-carboxaldehydes ( 5 ) when treated with sodium ethoxide in an aprotic polar solvent at room temperature. The 6-cyano analogue ( 18 ) also underwent ring transformation under the same mild conditions giving 7-amino-8-ethyl-5,8-dihydro-5-oxopyrido[2,3-d]pyrimidine-6-carboxaldehyde ( 21 ). However, the ring transformations of the pyrido[2,3-d]pyrimidine bearing no N₈-substituent ( 12 ), ethyl 1-ethyl-1,4-dihydro-4-oxo-1,8-naphthyridine- ( 14 ) and -quinoline-3-carboxylates ( 16 ) failed to occur. A mechanism is discussed.     

Dioxodihydrobenzo[b]furoindoles

The synthesis and some properties of the isomeric 2,3-dioxo-2,3-dihydro-1H-benzo[b]furo[2,3-g]- and 2,3-dioxo-2,3-dihydro-1H-benzo[b]furo[3,2-g]indoles are described. Georgian Technical University, Tbilisi 380075. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, 627–630, May, 1999.     

An efficient synthesis of functionalized tetrahydro-lH-indeno[2, 1-c]pyridine derivatives by a PPh3-promoted condensation reaction between acetylene esters and 1,3-dioxo-N-aryl-2,3- dihydro-1 H-indene-2-carboxamides

A reaction between 1,3-dioxo-N-aryl-2,3-dihydro-lH-indene-2-carboxamides, dialkyl acetylenedicar- boxylates, and triphenylphosphine or trimethylphosphite is described as a simple and efficient method for the synthesis of 5-hydroxy-4-aryl-2,5-dihydrofuran-2,3-dicarboxylate derivatives.     

Reaction of 2-bromomethyl-1,3-thiaselenole with thiourea: en route to the first representatives of 2-(organylsulfanyl)-2,3-dihydro-1,4-thiaselenines

The regioselective reaction of 2-bromomethyl-1,3-thiaselenole 1 with thiourea is accompanied by rearrangement, expanding the ring to afford the corresponding six-membered isothiuronium salt, 2-[amino(imino)methyl]sulfanyl-2,3-dihydro-1,4-thiaselenine hydrobromide 2, a synthon of the 2,3-dihydro-1,4-thiaselenin-2-ylthiolate anion. The latter was used for the synthesis of the first representatives of 2-(organylsulfanyl)-2,3-dihydro-1,4-thiaselenines 3a–g, bis(2,3-dihydro-1,4-thiaselenin-2-yl) disulfide 5 and 1,6-bis(2,3-dihydro-1,4-thiaselenin-2-ylsulfanyl)hexane 6.