Double bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene to 5-ethylidenebicyclo[2.2.1]hept-2-ene over alkaline earth oxides

All the alkaline earth oxides exhibit activities for double, bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene (VBH) to 5-ethylidenebicyclo[2.2.1]hept-2-ene (EBH) at a reaction temperature of 273 K. The order of the activity on the basis of unit weight of catalyst was CaO>MgO>SrO>BaO when compared under optimum pretreatment conditions. The E/Z ratio in the products is determined by the reaction temperature regardless of the type of catalyst; the ratios were 82/18 and 88/12 for the reaction temperatures of 323 and 273 K, respectively.     

TRITHIA-DIPHOSPHABIYCLO[2.2.1]HEPTANE

Abstract

3,6-Dialkyl-2,5-Dithioxo-1,4,2λ⁵,5λ⁵-dithiadiphosphorinan-2,5-disulfides (1) react with PSCI₃, to give 3,6-Dialkyl(diaryl)-1,4-dithioxo-2,5,7-trithia-lλ⁵,4λ⁵ diphosphabicyclo[2.2.1]heptanes (2). The reaction mechanism of their formation. and the stereochemistry are discussed. By reduction of 2 with (n-C₄H₉)₃P or (C₆H₅),P 3,6-Dialkyl-2,5,7-trithia-1λ³,4λ³-diphosphabicyclo[2.2.1]heptanes (3) are formed. 2c reacts with one mole of (C₆H₅)₃P to give 3,6-Diethyl-l-thioxo-2,5,7-trithia-lλ⁵,4λ³- diphosphabicyclo(2.2.1]heptane, 4c.

3,6-Dialkyl-2,5-dithioxo-1.4,2λ⁵,5λ⁵-dithiadiphosphorinan-2,5-disulfide (I) reagieren mit PSCI₃ zu 3,6-Dialkyl(diaryl)-1,4-dithioxo-2,5,7-trithia-lλ⁵,4λ⁵-diphosphabicyclo[2.2.l]heptanen (2). Der Reaktionsmechanismus ihrer Bildung und ihre Stereochemie werden diskutiert. Die Reduktion von 2 mit (n-C₄H₉)₃,P oder (C₆H₅)₃P führt zu 3,6-Dialkyl-2,5,7-trithia-1λ³,4λ³-diphosphabicyclo[2.2.1] heptanen(3). 2c reagiert mit einer äquimolaren Menge (C₆H₅)₃,P zu 3,6-Diethyl-l-thioxo-2,5,7-trithia-lλ⁵,4λ³- diphosphabicyclo[2.2.1]heptan, 4c.     

[2.2.1]-Bicyclic systems relevant to synthetic studies on CP-225,917—use of a new silylated cyclopentadiene

The [2.2.1]-bicyclic ketone 6, a potential synthetic precursor to CP-225,917, was prepared by a sequence beginning with Diels-Alder reaction between dimethyl fumarate and the silylated cyclopentadiene 38. The adduct 40 was subjected to Tamao-Fleming oxidation, which converted it into alcohol 21. During the oxidation BF₃·Et₂O-AcOH was used instead of the more expensive BF₃·2AcOH complex. Alcohol 21 was elaborated into 6, which carries one of the sidechains of CP-225,917, as well as other substituents that are appropriate for further elaboration.     

A Diels-Alder approach to trans-trisbicyclo[2.2.1]heptabenzene derivative

A new route to the synthesis of a trans-tris(bicyclo[2.2.1]hexeno)benzene derivative, using Diels-Alder reaction as critical step, was investigated. The compound with six methoxycarbonyl groups was successfully synthesized in good yield without any organometallic reagents. Some useful by-products from dimethyl but-2-ynedioate were also isolated from the last step. Perhaps due to stereo-hindrance or electrostatic repulsion in the cis-isomer, trans-isomer was found to be the only isomer in the crystal and its structure was proved by X-ray diffraction.     

Unusual reactivity of bicyclo[2.2.1]heptene derivatives during the ozonolysis

This paper describes mechanistic studies on the ozonolysis of bicyclo[2.2.1]heptene derivatives 6 and 7 obtained from (R)-(+)-pulegone through the cyclopentadiene 5 and its Diels-Alder reaction with maleic anhydride. The ozonolysis of the tricyclic diol 7 led to the ketone 8 with the same skeleton while the anhydride 6 gave rise to the epoxide 10 and the bis-lactone 11. The structure of 8, 10 and 11 are confirmed by X-ray analysis. These unexpected results are discussed in terms of a π complex between ozone and the double bond.     

Ozonolysis of bis-endo-diacylbicyclo[2.2.1]heptenes in dichloromethane-methanol

Ozonolysis of bis-endo-diacylbicyclo[2.2.1]heptenes 3a-d at −78 °C in dichloromethane-methanol gave the hydroperoxides 6a-d in 70-80% yields. Ozonolysis of bis-endo-diacetylbicyclo[2.2.2]octene 15 and bis-endo-diacetyl-7-oxabicyclo-[2.2.1]heptene 16 under the same reaction conditions gave the hydroperoxides 17 and 18, respectively. The intramolecular sequential nucleophilic addition of the carbonyl groups to the carbonyl oxide group was observed for the first time and was found to be faster than the intermolecular nucleophilic addition of a methanol molecule to the carbonyl oxide group. Ozonolysis of compound 23 in CH₂Cl₂-MeOH at −78 °C followed by reduction with Me₂S gave compounds 24 and 25, in which the stereochemistry of the methoxyl groups was determined by X-ray analysis.     

Unusual reactivity of bicyclo[2.2.1]heptene derivatives during the ozonolysis. Part 2

The ozonation of four bornene derivatives, prepared from (R)-(+)-pulegone, which possess a particularly hindered double bond, led to the formation of unexpected products depending on the nature of the solvent. The formation of the corresponding epoxides, ketones with the same skeleton, various lactones and even an allyl alcohol and an allyl chloride (allylic functionalisation) was observed. In two cases, products presenting a pulegone modified skeleton resulting from a Wagner-Meerwein rearrangement were obtained. The structure of three products was confirmed by crystallographic X-ray analysis. Mechanisms taking into account the rigid and congested structure of the reactants explain these results. The most striking steps were backed up by theoretical calculations.     

Novel rhodium catalyst for asymmetric hydroformylation of styrene: Study of electronic and steric effects of phosphorus seven-membered ring ligands

The asymmetric hydroformylation of styrene catalysed by rhodium complexes modified by monodentate phosphepine ligands has been investigated. The effects of a systematic variation of the phosphorus substituent on catalytic activity and selectivity are reported as well as the outcome of a combinatorial approach for the formation of mixed ligands complexes with several commercially available ligands. Effective catalytic systems have been devised for the reaction that provide for full conversion within 24 h and regioselectivity up to 96% in the branched aldehyde and enantioselectivities up to 48%. The use of bidentate ligands built up by binaphthyl-supported seven-membered phosphacyclic units does not allow for further improvement in the reaction outcome.     

氮杂炔正离子与环烯反应的机理及取代基效应

用DFT方法研究了氮杂炔正离子[R-C≡N-CH3] 与二环[2,2,1]-2-庚烯的反应机理。所有几何构型用B3LYP/6-31G**基组进行优化,过渡态通过振动分析和内聚反应坐标进行了确认。并在相同基组上研究了当R为不同取代基时的反应变化规律。结果表明该反应为环加成反应,有两条反应途径,产物主要通过能量较低的过渡态TSa生成。当取代基为支链烷烃基团时,反应位垒较大;取代基为直链烷烃基团和苯环时,反应较易进行。     

Synthesis and free radical polymerization of 2-methylene-7-oxabicyclo[2.2.1]heptane

A new monomer, 2-methylene-7-oxabicyclo[2.2.1]heptane ( IV ) was synthesized via four steps. Its structure was confirmed by IR, ¹H-NMR, and ¹³C-NMR spectra as well as elementary analysis. Free radical polymerization and copolymerization of IV were investigated. No homopolymer was obtained due to the effect of allyl inhibition. When IV copolymerized with electron-donor monomers, such as vinyl acetate and stvrene, IV acted as inhibitor for the polymerization of vinyl acetate, but could not inhibit the polymerization of styrene. However, the copolymers of IV with electron-accepting monomers, such as methyl methacrylate, acrylonitrile, or maleic anhydride (MA) were obtained. The contents of IV in the copolymers increased as e values of electron-accepting monomers increased. Strictly alternating copolymer was obtained only in the case of MA and IV . The thermal properties of copolymers were investigated. © 1995 John Wiley & Sons, Inc.     

High-Temperature Bromination XIII [1]: Bromination of Dimethyl 7-Oxabicyclo[2.2.1]hepta-2,5-diene-2,3dicarboxylate

The electrophilic addition of bromine to dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate 10 at 0 and –60°C led in high yield to the formation of dibromide 11. However, high-temperature bromination of 10 in carbon tetrachloride at 77°C gave four products 12–15, three of them with nonrearranged skeleton. Similarly, bromination of the dibromides 14 and 15 at 77°C yielded the nonrearranged tetrabromides 13 and 16, respectively. The structure of the tetrabromide 13 was solved by single-crystal X-ray analysis. The formation mechanism is discussed and supported by calculations.     

相转移催化合成7-氧杂双环[2.2.1]-庚-5-烯-2,3-二酰亚胺N-烃基衍生物

7-氧杂双环[2.2.1)-庚-5-烯-2,3-二酰亚胺的N-烃基衍生物是一类有生物活性的化合物。刘纪云等用相应的酸酐和各种胺类化合物在水或醇中反应合成了上述化合物,但收率较低。聚乙二醇(PEG)作为一种新的相转移催化剂在合成中广有应用。实验证明PEG     

A hybrid phosphorus ligand for highly enantioselective asymmetric hydroformylation

A new hybrid phosphorus ligand has been prepared starting from chiral NOBIN (2-amino-2'-hydroxy-1,1'-binaphthyl). Excellent enantioselectivities (up to 99% ee) have been achieved in the Rh-catalyzed asymmetric hydroformylations of styrene derivatives and vinyl acetate.     

Metathesis of spirocyclo[2.2.1]hept-2-ene-7,1'-cyclopropane

Metathesis of spirocyclo[2.2.1]hept-2-ene-7,1'-cyclopropane and its co-metathesis with norbornene and 5-decene on homogeneous and heterogeneous catalytic systems were carried out for the first time. The reactions were shown to proceed with retention of the spirosystem.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 138–139, January, 1993.     

Reaction of 2-azabicyclo[2.2.1]heptenes with nitrile oxides

The reaction of 2-azanorbornene derivatives with nitrile oxides (generated in situ by dehydrohalogenation of N-hydroxyimoyl halides) affords two regioisomers with the exo-arrangement of the isoxazoline ring.     

对映体纯1-甲基-7-氧杂双环[2.2.1]庚烷-2-酮的制备

1-甲基 - 7-氧杂双环 [2 .2 .1 ]庚烷 - 2 -酮 ( 1 )是萜类天然产物全合成中的重要中间体 ,能被广泛地应用于多种桉烷 ( Eudesmane)、沉香呋喃 ( Agarofuran)和降胡萝卜素 ( Norcarotenoids)等倍半萜天然产物的全合成[1,2 ] .我们以对映体纯化合物 1为原料 ,实现这类天然产物的不对称全合成 [3～ 6 ] .消旋的化合物 (± ) - 1可以 2 -甲基呋喃和 2 -氯丙烯腈为原料 ,经 3步反应得到 [2 ] .但对映体纯化合物 1的制备尚未见报道 .本文用化学拆分方法 ,成功地制备了对映体纯的 ( + ) - 1和 ( - ) - 1 ,并确定了其绝对构型 .1　结果与讨论为减…     

A practical synthesis of (1S,4S)-2,5-diazabicyclo[2.2.1]heptane

The rigid piperazine homologue 2,5-diazabicyclo[2.2.1]heptane (DBH) finds extensive application in medicinal chemistry and pharmaceutical research, but access to this scaffold is non-trivial. This letter details a concise synthetic sequence that gives ready access to DBH on gram scale. The route features a Staudinger reduction of an azide to facilitate a transannular cyclisation     

Desymmetrization of meso 7-aza-2,3-bis(phenylsulfonyl) bicyclo[2.2.1]hept-2-ene: a re-examination. Kinetic resolution of racemic 3-arylsulfonyl-7-aza-2-bromobicyclo[2.2.1]hepta-2,5-dienes

The inexpensive large scale preparation of N-methoxycarbonyl-7-aza-2,3-bis(phenylsulfonyl)bicyclo[2.2.1]hept-2-ene and the re-examination of its stereoselective desymmetrization are reported. Moreover, the kinetic resolution of N-protected 3-arylsulfonyl-7-aza-2-bromobicyclo[2.2.1]hepta-2,5-dienes promoted by (R,R)-hydrobenzoin is described, representing a new tool to fix the absolute stereochemistry of the 7-azabicyclo[2.2.1] skeleton.