3,4-Dimethoxyfuran: Eigenschaften,Berechnungen und Substitutionsreaktionen

3,4-Dimethoxyfuran: Properties, Calculations and some Substitution Reactions 3,4-Dimethoxyfuran (3,4-DF) is much more reactive than furan itself. We present experimental details for the synthesis of this useful compound in 50–100 g batches. 3-4-Dibenzyloxyfuran has also been prepared. Quantum mechanical calculations by PPP-and CNDO-methods analogous to furan itself gave the following information (compared with furan): enhanced negative partial charge at C(2) and C(5), higher acidity at α-position, a stronger and at the same time inverted dipol moment. In accordance with the calculations, 3,4-DF can easily be substituted by weak electrophilic reagents, e.g. in a typical Mannich reaction. The bis-amino compound 8 is produced in good yields. Lithiation by butyl-Li leads to mono- or di-substituted products. The mono- and di-Li-3,4-DF have been used for the preparation of various acylated and alkylated 3,4-DF derivatives. By acid hydrolysis of 3,4-DF crystalline 4-methoxy-3 (2H)-furanone has been prepared.     

Eine Synthese von Bicyclo[10.3.0]pentadec-1(12)-en-13-on und seinem 14-Methylderivat

A Synthesis of Bicyclo[10.3.0]pentadec-1(12)-en-13-one and its 14-Methyl Derivative. A new route to bicyclo[10.3.0]pentadec-1(12)-en-13-one ( 2 ) and its 14-methyl derivative 3 – useful intermediates in the synthesis of cyclopentadecanone ( 4 = exaltone®) and rac-muscone ( 5 ) – is described.     

Hydrierte Derivate von Benz[f]- und Benz[g]isochinolinen

Zusammenfassung Aus 1- und 2-(2-Aminoalkyl)-5,6,7,8-tetrahydronaphthalin wurden durch Ringschluß nachPictet—Spengler oderBischler—Napieralski hydrierte Benz[f]- und Benz[g]isochinoline gewonnen. Einzelne dieser Verbindungen zeigen beachtliche analgetische Wirkung.

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From 1- and 2-(2-aminoalkyl)-5,6,7,8-tetrahydronaphthalene, hydrogenated benz[f]- and benz[g]isoquinolines have been obtained by cyclization according toPictet—Spengler orBischler—Napieralski. Some of these compounds exhibit remarkable analgesic activity.

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Herrn Prof. Dr.H. Bretschneider zu seinem 60. Geburtstag gewidmet.     

Umwandlung von Bicyclo [3.2.0]hept-2-en-6-on in Cyclopentadienessigsäure-Derivate

Conversion of Bicyclo [3.2.0]hept-2-en-6-one into Cyclopentadienylacetic Acid Derivatives The reaction of a mixture of 4exo-bromobicyclo [3.2.0]hept-2-en-6-one ( 2 ) and -7-one ( 3 ) with O- or N-nucleophiles yielded cyclopentadien-5′-yl-acetates 4a–f or-acetamides 4g–h . Due to their rapid isomerization, the products 4 were not isolated, but some of them were demonstrated spectroscopically or captured in situ with maleimide as 10′-substituted norbornene derivatives 7 . The formation of 4 from 2/3 involves a fragmentation of the bond between the carbonyl and the bridge-head C-atom, induced by the attacking nucleophile and the leaving Br-ion and aided by the relief of the four-membered ring strain. Some of the isomerization products of 4 , i.e. the cyclopentadiene-1′-yl- and 2′-yl-acetyl derivatives were captured with maleimide as the 1′- and 8′-substituted norbornene-derivatives 8 and 9 . Two C-nucleophiles did not induce the fragmentation: sodium acetylacetonate substituted the Br-atom and sodium (diethoxyphosphoryl)ethoxycarbonylmethide condensed with the carbonyl group of 2/3 , yielding 11/12 and 13/14 , respectively.     

Zur Synthese sulfonierter Derivate von 2,3-Dimethylanilin und 3,4-Dimethylanilin

On the Synthesis of Sulfonated Derivatives of 2,3-Dimethylaniline and 3,4-Dimethylaniline Baking the hydrogensulfate salt of 2,3-dimethylaniline ( 1 ) or of 3,4-dimethylaniline ( 2 ) led to 4-amino-2,3-dimethylbenzenesulfonic acid ( 4 ) and 2-amino-4,5-dimethylbenzenesulfonic acid ( 5 ), respectively (Scheme 1). The sulfonic acid 5 was also obtained by treatment of 2 with sulfuric acid or by reaction of 2 with amidosulfuric acid. 3-Amino-4,5-dimethylbenzenesulfonic acid ( 3 ) and 5-Amino-2,3-dimethylbenzenesulfonic acid ( 6 ) were prepared by sulfonation of 1,2-dimethyl-3-nitrobenzene ( 9 ) to 3,4-dimethyl-5-nitrobenzenesulfonic acid ( 11 ) and of 1,2-dimethyl-4-nitrobenzene ( 10 ) to 2,3-dimethyl-5-nitrobenzenesulfonic acid ( 12 ), respectively, with subsequent Béchamp reduction (Scheme 1). Preparations of 2-amino-3,4-dimethylbenzenesulfonic acid ( 7 ) and of 6-amino-2,3-dimethylbenzenesulfonic acid ( 8 ) were achieved by the sulfur dioxide treatment of the diazonium chlorides derived from 3,4-dimethyl-2-nitroaniline ( 24 ) and from 2,3-dimethyl-6-nitroaniline ( 31 ) to 3,4-dimethyl-2-nitrobenzenesulfonyl chloride ( 29 ) and 2,3-dimethyl-6-nitrobenzenesulfonyl chloride ( 32 ), respectively, followed by hydrolysis to 3,4-dimethyl-2-nitrobenzenesulfonic acid ( 30 ) and 2,3-dimethyl-6-nitrobenzenesulfonic acid ( 33 ), and final reduction (Scheme 3). Compound 7 was also synthesized by reaction of 4-chloro-2,3-dimethylaniline ( 23 ) with amidosulfuric acid to 2-amino-5-chloro-3,4-dimethylbenzenesulfonic acid ( 20 ) and subsequent hydrogenolysis (Scheme 2). 4′-Bromo-2′, 3′-dimethyl-acetanilide ( 13 ) and 4′-chloro-2′, 3′-dimethyl-acetanilide ( 14 ) on treatment with oleum yielded 5-acetylamino-2-bromo-3,4-dimethylbenzenesulfonic acid ( 17 ) and 5-acetylamino-2-chloro-3,4-dimethylbenzenesulfonic acid ( 18 ), respectively. Their structures were proven by hydrolysis to 5-amino-2-bromo-3,4-dimethylbenzenesulfonic acid ( 21 ) and 5-amino-2-chloro-3,4-dimethylbenzenesulfonic acid ( 22 ), followed by reductive dehalogenation to 3 .     

7,15-Diazadispiro[5.1.5.3]hexadecan und Derivate, 3. Mitt.: Carbamidino- und Thiocarbamoylderivate von 14-Imino-7,15-diazadispiro[5.1.5.3]hexadecan

14-Imino-7,15-diazadispiro[5.1.5.3]hexadecane reacts with carbodiimides and isothiocyanates to form 11 adducts. The assumption, that additions take place at the 14-imino group, is supported by spectroscopic data.

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H. Egg, 2. Mitt., Mh. Chem.106, 1175 (1975)     

Reaktionen des 4-Bromo-1,6-methano[10]annulen-3-carbaldehyds: Synthese von 3,4-heteroanellierten 1,6-Methano[10]annulenen

Reactions of 4-Bromo-1,6-methano[10]annulene-3-carbaldehyde: Syntheses of 3,4-Heteroanellated 1,6-Methano[10]annulenes Similarly to β-chlorovinyl ketones, the title compound 1 reacts with dinucleophiles to give the 3,4-heteroanellated 1,6-methano[10]annulenes 2–4, 6 , and 12–16 , containing thiophene, pyrazole, pyrimidine, and thiazepine rings (Schemes 2 and 3). On reaction of 1 with tert-butylhydrazin, an unusual Michael-addition-dehydrogenation sequence, resulting in 2,3-anellation of a pyrazole ring (→ 5 ), is observed. Synthetic as well as some mechanistic aspects are briefly discussed.     

Die Dienol-Benzol-Umlagerung von Propargylcyclohexadienolen: aromatische [1,2]-, [3,3]- und [3,4]-sigmatropische Umlagerungen

The acid catalysed dienol-benzene rearrangement of methyl substituted o- and p-propargylcyclohexadienols ( 18–22 , 34 and 35 ) was investigated. In the first step water is eliminated to yield the corresponding methyl propargyl benzonium ions (cf. scheme 6, a ), which undergo [1s, 2s] sigmatropic rearrangements to give propargylbenzenes ( 28 , 29 , 30 , 38 ) and [3s, 4s] sigmatropic rearrangements to give allenylbenzenes ( 24–27 , 40) (cf. schemes 2, 3, 5, 6). [3s, 3s] sigmatropic rearrangements occur only to a small extend. In the rearrangement of 2-propargyl-2,4,6-trimethylcyclohexa-3,5-dien-1-ol ( 18 ) a [1s, 2s] sigmatropic methyl shift is observed (4%).     

Die Dienol-Benzol-Umlagerung von Allyldienolen: aromatische [1,2]-, [3,3]- und [3,4]-sigmatropische Umlagerungen

The dienol-benzene rearrangement of syn and anti-4-allyl-4-methylcyclohexa-2,5-dien-1-ol (syn and anti 15) occurs by formation of a benzonium ion intermediate in p-toluene-sulphonic acid in ether below 0° and leads to a mixture of 2-, 3- and 4-allyltoluenes in the ratio 54:10:36. By the introduction of ¹⁴C-, D- and methyl labelled dienols it is shown that only the allyl group migrates and that this rearrangement is an intramolecular, one-step process. The formation of 2-allyltoluene occurs with retention, whereas the 3- and 4-allyltoluenes are formed by inversion of the carbon skeleton of the migrating allyl group. These rearrangements can be therefore classified as suprafacial, aromatic sigmatropic reactions of the order [1,2], [3,3] and [3,4]. The transition state can be postulated as representing a positively charged complex consisting of interacting allyl and tolyl radicals. The interaction of the two parts is controlled by the symmetry of the highest occupied π-orbitals (ψ₃ for toluene and ψ₂ for the allyl group) in agreement with the Woodward-Hoffmann rules. The better “distribution” of the charge in the transition state of these reactions in comparison to the ground state is chiefly responsible for the CoPE-like [3,3] sigmatropic reaction occurring at low temperatures. In general, sigmatropic reactions in charged systems are faster. The rearrangement of syn and anti 2-allyl-2-methylcyclohexa-3,5-dien-1-ol (syn and anti 28) gives results similar to those obtained with the para-allyldienols. The thermal rearrangement of 15 and 28 gives 3-allyltoluene by a [3,3] sigmatropic Cope rearrangement followed by elimination of water.     

Thermische Umlagerung von 2-Oxa-bicyclo [3.3.1]-non-7-en-3-on; eine neuartige Lactonumlagerung. Vorläufige Mitteilung

Thermal Rearrangement of 2-Oxa-bicyclo [3.3.1]-non-7-en-3-ones; a Novel Lactone Rearrangement Lactone (+)- 2 was prepared by iodolactonisation and subsequent elimination in 51% yield from the known acid (+)- 1 (Scheme 1). Alkylation of (+)- 2 furnished (+)- 3a , (+)- 3b and (+)- 3c , respectively (Scheme 2). Heating of (+)- 3a in boiling DMF racemized the compound ((+)- 3a ? (?)- 4a ). Heating of (+)- 3b and (+)- 3c , respectively, equilibrated them with (?)- 4b and (?)- 4c , respectively. This results are interpreted as a [3.3]-sigmatropic rearrangement with a transition state as depicted in a .     

Pr4S3[Si2O7] und Pr3Cl3[Si2O7]: Durch weiche Fremdanionen modifizierte Derivate von Praseodymdisilicat

Pr₄S₃[Si₂O₇] and Pr₃Cl₃[Si₂O₇]: Derivatives of Praseodymium Disilicate Modified by Soft Foreign Anions For synthesizing both the disilicate derivatives Pr₄S₃[Si₂O₇] and Pr₃Cl₃[Si₂O₇], Pr, Pr₆O₁₁ and SiO₂ are brought to reaction with S and PrCl₃, respectively, in suitable molar ratios (850 °C, 7 d) in evacuated silica tubes. By using NaCl as a flux, Pr₄S₃[Si₂O₇] crystallizes as pale green, transparent single crystals (tetragonal, I4₁/amd, a = 1201.6(1), c = 1412.0(2) pm, Z = 8) with the appearance of slightly compressed octahedra. On the other hand, Pr₃Cl₃[Si₂O₇] emerges as pale green, transparent platelets and crystallizes monoclinically (space group: P2₁, a = 530.96(6), b = 1200.2(1), c = 783.11(8) pm, β = 109.07(1)°, Z = 2). In both crystal structures ecliptically conformed [Si₂O₇]^6– units of two corner‐linked [SiO₄] tetrahedra with Si–O–Si bridging angles of 131° in the sulfide and 148° in the chloride disilicate are present. In Pr₄S₃[Si₂O₇] both crystallographically independent Pr³⁺ cations show coordination numbers of 8 + 1 (5 S^2– and 3 + 1 O^2–) and 9 (3 S^2– and 6 O^2–). For Pr1, Pr2 and Pr3 in Pr₃Cl₃[Si₂O₇] coordination numbers of 10 (5 Cl^– and 5 O^2–) and 9 (2 ×; 4 Cl^– and 5 O^2– or 3 Cl^– and 6 O^2–, respectively) occur.