An innovative synthesis of dibenzofurans through a carbanion-induced ring transformation reaction

An innovative route for the synthesis of substituted dibenzofurans has been delineated through a ring transformation reaction of suitably functionalized 2H-pyran-2-ones by reaction with 7-methoxybenzofuran-3-one, in high yield. The novelty of the procedure lies in the creation of an aromatic ring from a 2H-pyran-2-one involving the -COCH₂-moiety of the substrate.     

Potential non-steroidal estrogens and antiestrogens,IV Organic azides in heterocyclic synthesis,part 13: Synthesis of aza- and diazacoumestrols via azido derivatives

Summary 4-Chloro-3-aryl-coumarins and quinolones2 a–e undergo thermolytic ring closure by reaction with sodium azide in refluxing dimethyl formamide to yield indolo[3,2-c]coumarins and indolo[3,2-c]quinolin-6(5H)-ones6 a–e. In the case of the coumarin2 a the azido coumarin5 can be isolated. The mono- and diazacoumestrol-dimethylethers6 a–c are converted into the coumestrol analogues7 a–c and their diacetyl derivatives8 a–c.

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Potentielle nichtsteroidale Östrogene und Antiöstrogene, 4. Mitt.: Organische Azide in der Heterocyclensynthese, Teil 13: Synthese von Aza- und Diazacumöstrolen über Azidzwischenstufen

Zusammenfassung 4-Chlor-3-arylcumarine und-chinolone2 a–e reagieren thermolytisch mit Natriumazid in siedendem Dimethylfomamid unter Ringschluß zu Indolo[3,2-c]cumarinen und Indolo[3,2-c]chinolin-6(5H)-onen6 a–e. Nur aus dem Cumarinderivat2 a kann das zwischenzeitlich gebildete Azidocumarin5 isoliert werden. Die so erhaltenen Mono- und Diazacumöstroldimethylether6 a–c werden in die entsprechenden Cumöstrole7 a–c und ihre Diacetylderivate8 a–c umgewandelt.

     

Oxidative cleavage of a tricyclic pyridone to a bicyclic lactam-dione

Two equivalents cf anhydrous m-chloroperbenzoic acid (m-CPBA) cleaved the pyridone ring of 10-(3-chlorophenyl)-6,8,9,10-tetrahydrobenzo[b][1,8]naph forming; the ten-membered lactam α-diketone 12-(3-chlorophenyl)-7,8,9,10-tetrahydropyrido[2,3-b]azecine-5,6,11(12H)-trione. Under aqueous conditions, one equivalent of m-CPBA and the same pyridone formed the lactam α-ketol 12-(3-chlorophenyl)-7,8,9,10-tetrahydro-6-hydroxypyrido[2,3-b]azecine-5,11(6H, 12H)-dio     

Extremely facile ring inversion and rearrangement in fluorobicyclo[2.1.0]pentanes

cis-1,2,3,4,5,5-Hexafluorobicyclo[2.1.0]pentane and 1,2,4,5-tetrafluorobicyclo[2.1.0]pentane have been synthesized from hexafluorobenzene. The former hydrofluorocarbon, which exists entirely in the endo configuration, rearranges to cis-1,2,3,3,4,5-hexafluorocyclopentene below room temperature (E_a = 21.9 kcal/mol, log A = 13.4). The latter undergoes degenerate ring inversion with extraordinary ease (ΔG^‡ = 6.8 ± 0.2 kcal/mol at −55 °C). Density functional calculations indicate that significant bonding between the bridgehead carbons is retained in the ring inversion transition state. Analogous calculations predict for hexafluorobicyclo[1.1.0]butane a considerably lower barrier for ring inversion and more 1,3-bonding in the transition state.     

Synthesis of 1-oxa-2-silacyclopentane derivatives via intramolecular nucleophilic attack at silicon

Metalation of (HSiMe₂)₃CH with lithium diisopropylamide (LDA) in THF gives (HSiMe₂)₃CLi, which reacts with ethylene oxide, propylene oxide, 1,2-epoxy butane, 1,2-epoxy pentane, 1,2-epoxy hexane, and epichlorohydrin to give the corresponding 1-oxa-2-silacyclopentane derivatives. Then, glycidylmethacrylate (GM) random copolymers with styrene (St) (in a 1:1 and 1:3 mol ratio) were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. Both types of copolymers were treated with (HSiMe₂)₃CLi to give new modified copolymers. The reaction of (HSiMe₂)₃CLi with epoxides on the side chains of the copolymers does not lead to intramolecular nucleophilic attack contrary to simple epoxides. All the products have been characterized by spectroscopic techniques.     

Regioselective cleavage of the bis-benzylidene acetal of d-mannitol under oxidative and reductive conditions: a new approach to C2-symmetric chiral ligands

A highly regioselective oxidative cleavage of 1,3:4,6-di-O-benzylidene-d-mannitol was carried out using NBS and the resultant product was readily converted to the C₂-symmetric chiral ligand, (R,R)-3,4-dihydroxy-1,5-hexadiene. On the other hand, reductive cleavage of 1,3:4,6-di-O-benzylidene-d-mannitol was achieved in a highly regioselective manner using BF₃·OEt₂ and Et₃SiH to give a highly functionalized benzyl ether, which was converted to a synthetically useful C₂-symmetric bis-amino alcohol derivative.     

Ring opening of 2-(cyanomethyl)aziridines by acid chlorides: synthesis of novel 4-amino-2-butenenitrile derivatives through intermediate aziridinium salts

1-Arylmethyl-2-(cyanomethyl)aziridines were transformed into novel N-arylmethyl-N-(2-chloro-3-cyanopropyl)amides as the major reaction products upon treatment with acid chlorides in CH₂Cl₂ through the ring opening of intermediate aziridinium salts. Subsequently, N-arylmethyl-N-(2-chloro-3-cyanopropyl)amides were converted into stable N-arylmethyl-N-(3-cyano-2-propenyl)amides for the first time by means of a dehydrochlorination mediated by Et₃N in CH₂Cl₂.     

Ph2S2-CaH2 in N-methyl-2-pyrrolidone as an efficient protocol for chemoselective cleavage of aryl alkyl ethers

CaH₂ was been found, for the first time, as a mild reducing agent to generate thiophenolate anion from Ph₂S₂ in N-methyl-2-pyrrolidone (NMP) for deprotection of aryl alkyl ethers. Excellent chemoselctivity was observed for substrates having chloro and nitro groups without displacement of the chlorine atom and the nitro group. Selective ether cleavage took place in the presence of α,β-unsaturated carbonyl and nitro groups without reduction and conjugate addition (to the α,β-unsaturated carbonyl group).     

The Efficient Synthesis of the Optically Active β‐Hydroxyl‐γ‐Butyrolactone Derivatives

The optically active β‐hydroxyl‐γ‐butyrolactones were synthesized from nonchiral starting material by employing reductive cleavage reaction, sharpless asymmetric epoxidation and dihydroxylation, and Lewis acid‐catalysed cyclization as key steps. This strategy can be used to prepare many chiral β‐hydroxyl‐γ‐butyrolactone analogues.     

硫杂蒽酮类稀土配合物的合成、表征及与DNA的作用(I)

合成了新的O-(硫杂蒽酮-[2]-基)-氧乙酸及其稀土配合物. 通过元素分析, IR, ¹H NMR, UV, DTA-TG和¹³C NMR谱对其结构进行了表征. 研究表明: 配体羧羰基脱质子后与金属离子配位, 2位氧原子也与金属离子配位, 配合物中含有一定量的配位水, 配合物为非电解质类型. 同时, 研究了O-(硫杂蒽酮-[2]-基)-氧乙酸稀土配合物对质粒DNA的切割作用. 结果表明: 铕的配合物对DNA的切割较明显, 且当配合物浓度增加时, 质粒DNA的超螺旋构型逐渐减少, 而缺刻、开环型构型逐渐增多. 在相同条件下, Eu(III)离子对质粒pBR322DNA几乎没有切割作用; 配体O-(硫杂蒽酮-[2]-基)-氧乙酸对质粒pBR322DNA也有切割作用, 但配合物EuL₃对质粒pBR322DNA的切割作用明显强于配体, 表明稀土离子Eu(III)与配体生成配合物后有较好的协同切割作用.