Reaction of diazoalkanes with unsaturated compounds. 10. 1,3-Dipolar cycloaddition of diazocyclopropane to strained cycloalkenes

The reaction of diazocyclopropane, generated in situ by alkaline hydrolysis of N-nitroso-N-cyclopropylurea at –20 to –40C, with the double bond of norbornene hydrocarbons or 3,3-dimethylcyclopropene is a 1,3-dipolar cycloaddition and affords 45–70% yields of thermally stable 1-pyrazolines possessing a spiro-joined cyclopropane fragment. Methylenecyclopropane under the same conditions is a less effective and selective interceptor of diazocyclopropane, forming in 10% yields not only isomeric 1-pyrazolines but the corresponding product of cyclopropylization, dispiro[2.0.2.1]heptane.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1057–1062, May, 1991.     

Spatial arrangement of norbornanedicarboxylic acids N-arylimides

The effect of substituents on the spatial arrangement of norbornane compounds was investigated. Norbornanedicarboxylic acids N-arylimides with OCH₃, Cl, NO₂ groups in the ortho-position of the aromatic ring form as conformational isomers with hindered rotation. The specific spatial isomerism is confirmed by the quantum-chemical calculations.     

Cycloadditions of isoquinolinium N-arylimides to enamines

The azomethine imine group of isoquinolinium N-arylimides 2 is partially incorporated into an aromatic ring. The nucleophilic-electrophilic 1,3-dipoles 2 undergo cycloadditions to ethylene derivatives bearing either electron-withdrawing or electron-releasing substituents. The regiochemistry is bidirectional; electron-attracting substituents appear at the 1-position of the tricyclic adducts. Various enamines, however, adopt an orientation such that the amino function appears at the 2-position. The tricyclic adducts undergo an acid-catalyzed hyrazo rearrangement.     

Ring opening-cross metathesis of unstrained cycloalkenes

Unstrained cycloalkenes undergo ruthenium-catalysed ring opening-cross metathesis reactions with simple alpha, beta-unsaturated carbonyl compounds under mild conditions.     

Proton spin coupling constants in cycloalkenes

The proton-proton coupling constants in cyclopentadiene, cyclohexadiene, cycloheptatriene, cyclooctatetraene, cyclopentene and cyclohexene have been calculated using the finite perturbation INDO method. The carbon geometry was taken from the corresponding electron diffraction studies. The theory gives satisfactory agreement with experiment. In terms of the many factor structural model, distance and angle distortions have been studied in ethylene, cis-1,3-butadiene and cis-2-butene. It has been established that these distortions produce noticeable changes only for those protons whose co-ordinates are changed. The coupling constants across three, four and five bonds are discussed separately in connection with the structural factors and the σ–π contribution. Finally, variations in the proton co-ordinates in cyclopentadiene are used to optimize the proton couplings.     

Regioselective ozonolytic cleavage of unsymmetric cycloalkenes

Aldehyde 2 was prepared in a one-pot sequence from olefin 12; olefin 6 did not react similarly. Possible reasons for the differences are discussed.     

Impact of neutral and acidic species on cycloalkenes nucleation

Non-covalent hydrogen bond interactions between the π cloud of cycloalkenes and three atmospheric common nucleation precursors (H₂S, H₂O, and MeOH) have been investigated using DFT and CCSD(T). The structures and the energies of the 1:1 and 1:2 adducts were computed with the B3LYP-D3 method. The analysis of the investigated electronic properties and geometric parameters shows that cyclohexene is a stronger hydrogen bond acceptor than cyclopentene, then followed by 1,4-cyclohexadiene and 1,3-cyclohexadiene. Comparable red shifts of the OH-/SH-stretching vibrational frequencies were noticed for the studied clusters. Increasing the ring size enhances the hydrogen bond interaction, and increasing the π delocalization decreases the hydrogen bond interactions. This is further confirmed by Bader’s quantum theory of atoms in molecules. The nonadditivity effects were observed in the trimolecular complexes. All the complexes were analyzed by energy decomposition analysis to divide the interaction energy into individual components. Furthermore, the dipole moments and atmospheric implications were also investigated.

     

Aluminum oxide catalyzed isomerization of acylated cycloalkenes

A homologous series of cyclic olefins and their corresponding 1-methyl derivatives were acylated using acetic anhydride/zinc chloride system. The resulting mixtures were, after appropriate analysis, isomerized quantitatively to the conjugated enones by adsorption on neutral alumina. A detailed, general experimental procedure is given.     

Isoquinolinium Fluorochromate: A New and Efficient Oxidant for Organic Substrates

Isoquinolinium fluorochromate is a versatile reagent for the effective and selective oxidation of organic substrates, in particular for alcohols, under mild conditions.     

Ozonolytic cleavage of cycloalkenes to terminally differentiated products

Conditions are reported which convert cycloalkenes to terminally differentiated products through the intermediacy of α-alkoxy hydroperoxides.     

Ru-catalyzed cyclization of terminal alkynals to cycloalkenes

Cycloalkenes can be efficiently prepared by a new Ru-catalyzed cyclization of terminal alkynals. Under appropriate conditions, cycloisomerizations to conjugated aldehydes may be observed. Both processes involve catalytic Ru vinylidenes.     

Ozonolytic cleavage of cycloalkenes to terminally differentiated products

A method is described by which alkoxy hydroperoxides, obtained by ozonising cycloalkenes in alcohol solution, can be converted into terminally differentiated products by the action of metal salts. Cyclohexene and cycloheptene were converted to 1,1-dimethoxy-5-chloropentane and 1,1-dimethoxy-6-chlorohexane respectively in 47% yield, using ferric chloride. With ferrous sulphate as reactant salt, cyclooctene was converted into 1,1-dimethoxy-6-heptene. A synthesis of (Z)-4-heptenal from (Z,Z)-1,5-cyclooctadiene is also described. Fragmentation, causing the loss of one carbon atom, is a characteristic of these transformations. Other variations employed the salts as oxidants and reductants simultaneously.     

通过异喹啉盐与环状1,3-二酮一锅合成二氢异喹啉-3-酮-1,4-桥环结构

异喹啉盐具有两个亲电位点, 用它与双亲核试剂发生去芳构化/环化反应, 是高效构建异喹啉桥环结构的有效策略. 然而, 这一策略主要集中在1,3-桥环结构的合成. 最近利用异喹啉盐与4-羟基香豆素反应, 首次实现了二氢异喹 啉-3-酮-1,4-桥环的合成. 但是, 当用环状1,3-二酮代替4-羟基香豆素反应时, 意外地得到了异喹啉-1,3,4(2H)-三酮. 利用高分辨质谱分析发现, 这一意外转化是由于环状1,3-二酮发生O-亲核取代后, 消除2-溴-1,3-环状二酮, 得到4-溴异喹啉-3(2H)-酮. 该中间体发生两次连续水解/空气氧化后, 得到了异喹啉-1,3,4(2H)-三酮. 基于此机理的认识, 向反应体系中添加催化量的三氟甲烷磺酸后, 成功抑制了环状1,3-二酮的O-亲核取代反应, 顺利得到了二氢异喹啉-3-酮的1,4-桥环结构(33个反应实例). 反应条件温和, 提供了一种构建异喹啉1,4-桥环骨架的高效合成方法.     

Adducts of phenoxathiin and thianthrene cation radicals with alkenes and cycloalkenes

Phenoxathiin cation radical perchlorate (PO.+ClO4(-)) added stereospecifically to cyclopentene, cyclohexene, cycloheptene, and 1,5-cyclooctadiene to give 1,2-bis(5-phenoxathiiniumyl)cycloalkane diperchlorates (4-7) in good yield. The diaxial configuration of the PO+ groups was confirmed with X-ray crystallography. Unlike additions of thianthrene cation radical perchlorate (Th.+ClO4(-)) to these cycloalkenes, no evidence for formation of monoadducts was found in the reactions of PO.+ClO4(-). This difference is discussed. Addition of Th.+ClO4(-) to five trans alkenes (2-butene, 2-pentene, 4-methyl-2-pentene, 3-octene, 5-decene) and four cis alkenes (2-pentene, 2-hexene, 2-heptene, 5-decene) gave in each case a mixture of mono- and bisadducts in which the configuration of the alkene was retained. Thus, cis alkenes gave erythro monoadducts and threo bisadducts, whereas trans alkenes gave threo monoadducts and erythro bisadducts. In these additions to alkenes, cis alkenes gave predominantly bisadducts, while trans alkenes (except for trans-2-butene) gave predominantly monoadducts. This difference is explained. 1,2-Bis(5-phenoxathiiniumyl)cycloalkanes (4-7) and 1,2-bis(5-thianthreniumyl)cycloalkanes underwent fast elimination reactions on activated alumina forming, respectively, 1-(5-phenoxathiiniumyl)cycloalkenes (8-11) and 1-(5-thianthreniumyl)cycloalkenes (12-16). Among adducts of Th.+ClO4(-) and alkenes, monoadducts underwent fast ring opening on alumina to give (5-thianthreniumyl)alkenes, while bisadducts underwent fast eliminations of H+ and thianthrene (Th) to give (5-thianthreniumyl)alkenes also. Ring opening of monoadducts was a stereospecific reaction in which the configuration of the original alkene was retained. Thus, erythro monoadducts (from cis alkenes) gave (E)-(5-thianthreniumyl)alkenes and threo monoadducts (from trans alkenes) gave (Z)-(5-thianthreniumyl)alkenes. Among bisadducts, elimination of a proton and Th occurred and was more complex, giving both (E)- and (Z)-(5-thianthreniumyl)alkenes. These results are explained. Configurations of adducts and (5-thianthreniumyl)alkenes were deduced with the aid of X-ray crystallography and (1)H and (13)C NMR spectroscopy. In the NMR spectra of (E)- and (Z)-(5-thianthreniumyl)alkenes, the alkenyl proton of Z isomers always appeared at a lower field (0.8-1.0 ppm) than that of E isomers.     

Highly diastereoselective epoxidation of allyl-substituted cycloalkenes catalyzed by metalloporphyrins

Highly diastereoselective epoxidations of allyl-substituted cycloalkenes including allylic alcohols, esters, and amines using sterically bulky metalloporphyrins [Mn(TDCPP)Cl] (1) and [Ru(TDCPP)CO] (2) as catalysts have been achieved. The "1 + H(2)O(2)" and "2 + 2,6-Cl(2)pyNO" protocols afforded trans-epoxides selectively in good yields (up to 99%) with up to >99:1 trans-selectivity.     

The Synthesis of 1,2-Bis(phenylsulfonyl)cycloalkenes

Reaction of the 2-(phenylthio)cycloalkanones 11–13 with thiophenol and chlorotrimethylsilane afforded the 1,2-bis(phenylthio)cycloalkenes 8–10 together with the corresponding 2,3-isomers 15–17 respectively. Treatment of compounds 7–10 with hydrogen peroxide in acetic acid gave the 1,2-bis(phenylsulfonyl)cycloalkenes 1–4.     

Divergent stereoselectivity in the photoaddition of alkanals and medium ring cycloalkenes

Photocycloaddition of alkanals and cycloheptene, cyclooctene, and 1,5-cyclooctadiene results in stereoisomeric oxetanes, the composition of which depends on the concentration of starting alkene.