Synthesis of a novel ferrocene derivative having flame-retardant and smoke-suppressant properties

Reaction of ferrocene with chlorendic anhydride (1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylic acid anhydride) under Friedel–Crafts reaction conditions affords a new monosubstituted dervative of ferrocene which has significant flameretardant and smoke-suppressant properties when incorporated into poly(vinyl chloride) (PVC). The monocarboxylic acid from the above reaction undergoes smooth methylation with diazomethane to give the corresponding methyl ester. ¹H and ¹³C NMR spectra of these compounds have been compared with those obtained from similar compounds, namely β-ferrocenoylpropanoic acid and its methyl ester. Distant asymmetric centres in the chlorendic anhydride substituent markedly affect the proton spectra of the ferrocene derivative.     

Lactonization of epoxyendic anhydride in reactions with amines

Reactions of exo-5,6-epoxybicyclo[2.2.1]hept-5-ene-endo-2,endo-3-dicarboxylic anhydride (epoxyendic anhydride) with acyclic, aromatic, heteroaromatic, and nonaromatic heterocyclic amines afforded the corresponding heterocyclization products, substituted exo-2-hydroxy-5-oxo-4-oxatricyclo[4.2.1.0^3,7]nonane-endo-9-carboxamides (oxabrendanes), whose structure was confirmed by the IR and ¹H and ¹³C NMR (including two-dimensional) spectra. Other approaches to the tricyclic compounds were also examined, in particular via reactions of organic peroxy acids with amido acids obtained by aminolysis of endic anhydride.     

Synthesis of polychlorinated mono- and bisimides of cyclic dicarboxylic acids containing diene-dienophile fragments

Polychlorinated diene-dienophile mono- and bisimides formed at the acylation of N-aminoimides of 1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-2,3- and endo,exo-1,2,3,4,11,11-hexachlorotricyclo[6.2.1.0^5,10]-undec-2-ene-7,8-dicarboxylic acids with maleic anhydride in DMF.     

Kinetic studies of inverse electron demand Diels–Alder reactions (iEDDA) of norbornenes and 3,6-dipyridin-2-yl-1,2,4,5-tetrazine

Inverse electron demand Diels–Alder additions (iEDDA) between 1,2,4,5-tetrazines and olefins have recently found widespread application as a novel ‘click chemistry’ scheme and as a mild technique for the modification of materials. Norbornenes are, due to their straightforward synthetic availability, especially interesting in the latter context. Therefore, the reactivity of different norbornene-based compounds was compared with unsubstituted norbornene and other alkenes using UV-vis measurements for the determination of reaction rates under pseudo first order conditions. Thereby, exo,exo-5-norbornene-2,3-dimethanol was found to be almost as reactive as unsubstituted norbornene whereas (±)-endo,exo-dimethyl-5-norbornene-2,3-dicarboxylate reacted only insignificanty faster than unstrained alkenes.     

Stereocontrolled approaches to 9(0)-methanoprostacyclin

A stable PGI₂ analog (methanoprostacyclin $\text{2}$) was synthesized starting from 5-norbornene-2,3-dicarboxylic anhydride.     

Epoxidation of Bicyclo[2.2.1]hept-5-ene-2,3-endo- and Exodicarboxylic Acid N-Arylimides

Epoxidation of endo- and exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid N-arylimides with a solution of peracetic acid in anhydrous dioxane affords 5,6-exo-epoxybicycloheptanedicarboxylic acid N-arylimides. The epoxidation reaction is not sensitive to the configuration of the imide fragment, to the character and position of the substituent in the aromatic ring. The reaction is determined only by oxidation conditions.     

The Gould-Jacobs Reaction of5-Aminoquinoxaline

 Reaction of 5-aminoquinoxaline with alkoxymethylene derivatives affords the corresponding quinoxalinoaminoethylenes. These undergo a thermal cyclization to yield angularly annelated 10H-pyrido[2,3-f]quinoxalines. The structures of all products were deduced from their IR, UV, mass, ¹H, and ¹³C NMR spectra.     

Lactonation of <Emphasis Type="Italic">N</Emphasis>-alkyl-and <Emphasis Type="Italic">N,N</Emphasis>-dialkylamido acids of norbornene series in reactions with performic acid

Reaction products were obtained from bicyclo[2.2.1]hept-5-ene-endo,endo-2,3-dicarboxylic (endic) acid anhydride and ammonia, methyl-, benzyl-, dimethyl-, methylbenzyl-, dibenzyl-, diethyl-, dipropyl-, diisopropyl-, and dipentylamines. The synthesized amido acids were subjected to epoxidation by organic peracids. The structure of compounds obtained was confirmed by IR, ¹H and ¹³C NMR spectra, and in some instances, by X-ray diffraction analysis.     

Cage-like amines in the synthesis and oxidation of camphor-10-sulfonic acid amides

Reactions of bicyclo[2.2.1]hept-5-en-exo- and -endo-2-ylmethanamines, exo-5,6-epoxybicyclo-[2.2.1]hept-exo-2-ylmethanamine, 1-(bicyclo[2.2.1]hept-2-yl)ethanamine, and 1-(1-adamantyl)ethanamine with camphor-10-sulfonyl chloride in chloroform in the presence of triethylamine gave the corresponding sulfonamides having two cage-like fragments. Stereoisomeric N-(bicyclo[2.2.1]hept-5-en-2-ylmethyl)camphor-10-sulfonamides were oxidized with peroxyphthalic acid generated in situ from phthalic anhydride and 50% hydrogen peroxide. The exo stereoisomer was thus converted into the corresponding 5,6-epoxy derivative, while the endo isomer gave rise to 4-(7,7-dimethyl-2-oxobicyclo[2.2.1]hept-1-ylmethyl)-4-azatricyclo[4.2.1.0^3,7]-nonan-exo-2-ol (substituted azabrendane). The structure of the synthesized camphor-10-sulfonamides was confirmed by IR and ¹H and ¹³C NMR spectra with the use of homo- (COSY) and heteronuclear ¹H-¹³C correlation techniques (HMQC, HMBC). Heterocyclization of sulfonamides of the norbornene series was also simulated by quantum-chemical calculations at the PM3 and BHandHLYP/6-31G(d) levels of theory.     

Orbital control of stereochemistry in acid-catalysed addition reactions of endo -tricyclo[3.2.1.02,4]0ct-6-ene

The reaction of endo-tricyclo[3.2.1.0^2,4]oct-6-ene 1 with methanol in the presence of catalytic amounts of toluene-p-sulphonic acid has been shown to give 2-exo- and endo-methoxybicyclo[3.2.1]oct-3-ene (2c) and (2d) and 2-endo-methoxybicyclo[3.2.1]oct-6-ene (13). The formation of 2-exo- methoxybicyclo[3.2.1]oct-3-ene (2c), the major product of reaction, has been probed by deuterium labelling experiments and a series of 6-exo-7-exo- dideuterobicyclo[3.2.1]oct-3-enes synthesised for ²H, ¹H and ¹³C NMR spectral analysis in order unambiguously to determine the stereochemistry of proton attack on endo-tricyclo[3.2.1 0^2,4]oct-6-ene (1). The formation of 2-exo-methoxybicyclo[3.2.1]oct-3-ene (2c) has been determined to involve corner protonation of the cyclopropyl moiety and skeletal rearrangement to an allylic cation with a small but measurable memory effect     

The Gould-Jacobs Reaction of5-Aminoquinoxaline

Summary.  Reaction of 5-aminoquinoxaline with alkoxymethylene derivatives affords the corresponding quinoxalinoaminoethylenes. These undergo a thermal cyclization to yield angularly annelated 10H-pyrido[2,3-f]quinoxalines. The structures of all products were deduced from their IR, UV, mass, ¹H, and ¹³C NMR spectra. Received September 24, 1999. Accepted November 18, 1999     

Stereochemical studies. 58. Saturated heterocycles. 39. Preparation and steric structures of dihydro-1,3-oxazines, 1,3-oxazin-2-ones and 1,3-oxazine-2-thiones fused with norbornane and norbornene

3-endo-Aminobicyclo[2.2.1]hept-5-ene-2-endo-carboxylic acid ( 1 ), prepared from endo-norborn-5-ene-2,3-dicarboxylic acid anhydride, and the analogous saturated cis-exo-amino acid ( 3 ) were reduced with lithium aluminum hydride to the aminoalcohols 2 and 4 ; the latter were cyclized by means of arylimino ethers to methylene-bridged tetrahydro- ( 6a-c ) and hexahydro-3,1-benzoxazines ( 7b-d ), respectively. The endo ( 2 ) and exo ( 4 ) aminoalcohols were converted to methylene-bridged tetrahydro-3,1-benzoxazin-2-one ( 9 ) and hexahydro-3,1-benzoxazin-2-one ( 12 ) with ethyl chloroformate and sodium methoxide; treatment of the alcohols with carbon disulfide gave, via the dithiocarbamates, the corresponding 2-thiones ( 11, 13 ). The structures were confirmed by ir and nmr spectroscopy.     

The π-Anisotropy of the Double Bond of a syn-11-Oxasesquinorbornene Derivative.. Stereoselectivity of the Diels–Alder additions of (2-norborneno)[c]furan. Crystal structure of 11-oxa-endo-tetracyclo[6.2.1.13,6.02,7]-dodec-2(7)-ene-9,10-exo-dicarboxylic anhydride

The reaction of (2-norborneno)[c]furan ( 4 ) with maleic anhydride gave 11-oxa-endo-tetracyclo[6.2.1.1^3,6.0^2,7]dodec-2(7)-ene-9,10-exo-dicarboxylic anhydride ( 5 ) and, with methyl acetylenedicarboxylate, methyl 11-oxa-endo-tetracyclo [6.2.1.1^3,6.0^2,7]dodeca-2(7),9-diene-9,10-dicarboxylate ( 7 ). The syn-11-oxa-sesquinorbornenes 5 and 7 could be equilibrated with their cycloaddents. They are at least 2 kcal/mol more stable than the corresponding anti-sesquinorbornenes 6 and 8 . The structure of 7 was deduced from its spectral data, by epoxidation with air or a peracid to give the exo-epoxide 13 and by catalytic hydrogenation to give 14 . The structure of 5 was established by single-crystal X-ray diffraction. A dihedral angle of 163° was measured between the C(1,2,7,8) and C(2,3,6,7) planes in 5 . This important deviation from planarity for the C(2,7) double bond is attributed to (π, ω)-repulsive interactions that make the π-electron density of 2-norbornene and 7-oxa-2-norbornene derivatives preferentially polarized toward the exo-face. This finding is discussed in relation with the relative stability of the syn- and anti- 11-oxasesquinorbornenes and with the endo-stereoselectivity of the cycloadditions of the norbornenofuran 4 .     

High pressure and thermal Diels-Alder reactions of 5-nitro[2.2]paracyclophanepyran-6-one

The Diels-Alder reactions of 5-nitro[2.2]paracyclophanepyran-6-one with 1,3-butadienes and 1,2-dihydro-3-vinyl-naphthalene were examined under thermal and high-pressure conditions. The cycloadditions with 1,3-butadienes occurred in good yield and anti-exo diastereoselectively only under high-pressure conditions; the one with 1,2-dihydro-3-vinyl-naphthalene afforded comparable yields of mixtures of anti/syn adducts under normal and high-pressure conditions. A structural analysis of the reaction products by ¹H and ¹³C NMR spectroscopy is presented.     

Correct structures of Diels-Alder adducts from the natural cyclolignan thuriferic acid and its 8-epimer

A detailed analysis of one- and two-dimensional ¹H and ¹³C NMR data for the endo and the exo adducts, obtained by Diels-Alder reaction of thuriferic and epithuriferic acids with cyclopentadiene is described. The unequivocal spectral data assignment of the endo and exo structures was complemented with molecular modelling studies and confirmed through X-ray diffraction studies.     

An expedient approach to tetrahydrofuro[3,2-b]pyridine-2(3H)-ones via activation of pyridine N-oxide by triflic anhydride

The double addition of bis(trimethylsilyl) ketene acetals [R₁, R₂ = CH₃, -(CH₂)₅-] to pyridine N-oxide promoted by triflic anhydride under mild conditions generates N-[(trifluoromethane)sulfonyl-1,2-dihydropyridine-2,4-dicarboxylic acids 2a-b. Subsequent reaction of these acids upon iodolactonization conditions affords tetrahydrofuro[3,2-b]pyridine-2(3H)-ones 3a-b containing an exo-insaturation on the products as a result of an unexpected decarboxylation.     

New synthetic approach to substituted isoindolo[2,1-a]quinoline carboxylic acids via intramolecular Diels-Alder reaction of 4-(N-furyl-2)-4-arylaminobutenes-1 with maleic anhydride

Acylation of substituted 4-(furyl-2)-4-arylaminobut-1-enes with maleic anhydride provided 2-allyl-6-carboxy-4-oxo-3-aza-10-oxatricyclo[5.2.1.0^1,5]dec-8-enes in high yield under mild reaction conditions. The Diels-Alder adducts are formed via an initial amide formation followed by a stereoselective intramolecular [4+2] exo-cycloaddition reaction. Treatment of the tricyclic compounds with phosphoric acid at high temperatures (70-120 °C) promoted cyclic ether opening, intramolecular cyclization and aromatization to give the corresponding tetracyclic compounds, 5,6,6a,11-tetrahydro-10-carboxyisoindolo[2,1-a]quinolines, in moderate yields. The influence of the acid and the reaction temperature on the cyclization reactions are also discussed.     

The intercalation of bicyclic and tricyclic carboxylates into layered double hydroxides

Twenty-four nanocomposites built from layered double hydroxides and bicyclic and tricyclic carboxylates have been synthesised for the first time. Eight carboxylates were successfully intercalated into [LiAl₂(OH)₆]Cl·yH₂O, [Ca₂Al(OH)₆]NO₃·yH₂O, and [Mg₂Al(OH)₆]NO₃·yH₂O, and the products fully characterised. Guest species incorporated include 1-adamantane carboxylate (1-AC) and 5-norbornene-2-endo-3-exo-dicarboxylate. In some cases, carbonate anions were co-intercalated with the organic guest, and in others poorly crystalline aluminium hydroxides formed as by-products. Sharper resonances were observed in the ¹³C solid-state NMR spectra of the 1-AC intercalates than in the spectrum of pure 1-AC, suggesting increased order in the arrangement of the cyclic cages in the intercalates. Where possible, time-resolved in situ X-ray diffraction was employed to study the nanoscopic steps involved in the intercalation reactions. These investigations showed that the reactions are one-step processes, proceeding directly to the fully exchanged intercalate with no intermediate phases. The intercalation processes were found to be nucleation controlled.     

Reactions of 4-amino-4-azatricyclo[5.2.1.0<Superscript>2,6-<Emphasis Type="Italic">endo</Emphasis></Superscript>]dec-8-ene-3,5-dione with dicarboxylic acid anhydrides

Reactions of 4-amino-4-azatricyclo[5.2.1.0^2,6-endo ]dec-8-ene-3,5-dione (hydrazinolysis product of endic anhydride) with succinic, maleic, cis-cyclohexane-1,2-dicarboxylic, endic, phthalic, and 1,8-naphthalic anhydrides were studied. Procedures for the preparation of the corresponding hydrazido acids and bis-imides were proposed. Their reactions with peroxyformic acid, depending on the substrate nature, led to the formation of both epoxy hydrazido acids and epoxy imides. The unsaturated adducts reacted with p-nitrophenyl azide to give the corresponding triazole derivatives.     

Controlling silica surfaces using responsive coupling agents

The surface chemistry of silica was modified using coupling agents capable of participating in oxidation or in the Diels-Alder (and retro Diels-Alder) reactions. The synthesis of the latter coupling agents, using trialkoxysilane groups linked to a cyclopentadiene structure, was achieved by the condensation of sodium cyclopentadienolide with 1-chlorodimethylsilyl-3-triethoxysilylpropane to give 1-cyclopentadienyldimethylsilyl-3-trialkoxysilylpropane. The cyclopentadiene ring in this structure was shown to undergo normal Diels-Alder chemistry with maleimides or maleic anhydride to give 7-(dimethylsilylpropyltrialkoxysilane)-5-norbornene-2,3-dicarboxylic acid anhydride. The retro Diels-Alder reaction of 7-(dimethylsilylpropyltrialkoxysilane)-5-norbornene-2,3-dicarboxylic acid anhydride in solution was not very efficient: the adduct is very stable and only undergoes the retro Diels-Alder reaction at temperatures in excess of 200 °C. Once grafted to the surface, however, the retro Diels-Alder reaction was achieved at a level greater than 90% by use of thermolysis in the presence of free cyclopentadiene. In addition, a polyene-based coupling agent derived from squalene was prepared by hydrosilylation using HMe₂SiOSiMe₂CH₂CH₂Si(OEt)₃. Once grafted to the surface, oxidation by ozone led to ozonides that could be reduced to ketone/aldehyde groups. These in turn could be trapped by functional groups such as hydrazines to make surface-bound hydrazones. With both types of coupling agents, the surface energy and nature of the functional groups bound to the surface could be changed on demand in response to an external stimulus.