Notiz zur Synthese von Alkyl-, Cycloalkyl- und Aryl-(4-aminophenyl)-sulfonen

Syntheses of Some Alkyl-, Cycloalkyl- and Aryl-(4-aminophenyl)-sulfones Syntheses of (4-aminophenyl)-alkyl, -cycloalkyl and -aryl sulfones 2 were achieved both by alkylation of 4-(acetylamino)-benzenesulfinic acid ( 7 ) to the corresponding acetanilides 9 followed by hydrolysis and by oxidation of the appropriate (4-nitrophenyl)-sulfides 11 to (4-nitrophenyl)-sulfones 1 with subsequent Béchamp reduction.     

Notiz zur Synthese von 1-Aryl- und 1-Alkyl-2, 3-dimethyl-chinoxaliniumperchloraten

Some 1-substituted 2, 3-dimethyl-quinoxalinium-perchlorates were synthesized by reaction of butane-2, 3-dion with N-monosubstituted 1,2-diamino-benzenes in strongly acidic solution. 2, 3-dimethyl-4-cyclohexyl-pyrido[2,3-b]pyraziniumperchlorate was obtained from an analogous reaction.     

Notiz zur Synthese von rac. cis- und trans-2-Nor-abscisinsäure

Note on the synthesis of rac. cis- and trans-nor-abscisic acid The synthesis of the 2-nor-analogues of cis- and trans-abscicic acid is described.     

Notiz zur Darstellung von Mono- und Di-Brompyridin

Ohne Zusammenfassung     

Notiz zur Synthese des Nonactins

With (?)-nonactic acid and the 8-epitosylate of benzyl (+)-nonactate usingWalden inversion (?)-nonactyl-(+)-nonactic acid is constructed. The latter forms by way of its imidazolide or its α-mercaptopyridyl ester the macrotetrolide nonactine in poor yield.     

Notiz zur quantitativen Bestimmung von Si-H- und Si-Si-Gruppen

Zusammenfassung Eine einfache und genaue Methode zur Bestimmung von Si-H- und Si-Si-Gruppen wird vorgeschlagen, die auf alkalischer Hydrolyse der Substanz in einem verschlossenen und evakuierten Kolben und AuswÄgen des dem entwickelten Wasserstoff entsprechenden Wasservolumens beruht. Bei H-Gehalten von 1–2% betrÄgt die Genauigkeit ± 0,03% (abs.).

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Note on the quantitative determination of Si-H- and Si-Si-groups

A simple, robust and surprisingly exact method for the quantitative determination of Si-H- or Si-Si-groups is based on alkaline hydrolysis of the Si-H- or Si-Si-containing substances in a sealed and evacuated vessel and weighing of the volume of water equivalent to the developed volume of hydrogen. The accuracy is ± 0.03% (abs.) with H contents of 1–2%.

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Herrn Prof. Dr. E. Asmus zum 60. Geburtstag gewidmet.     

Untersuchungen zur Basizität von Alkyl- und Silylakylaminen

Investigations on the Basicity of Alkyl and Silyl Alkylamines The basicity of N has been investigated in primary and secondary alkyl und silyl alkylamines by means of the v_C–D band shift of CDCl₃ associated to the amine group by potentiometrically determined pK_s-values, and by mass spectroscopically measured ionisation potentials. The results show a dependence on electronic and steric effects, but they do not give arguments for a conjugative interaction between N and Si,     

Versuche zur Synthese von Nonafulvenen und von Nonaheptafulvalen

Attempted Synthesis of Nonafulvenes and of Nonaheptafulvalene The reaction of cyclononatetraenide with α-bromobenzyl acetate ( 6 ) as well as with 1,1-dihalodimethylether gives at ?50°, instead of the expected cyclononatetraenes, bicyclo[6.1.0]nona-2,4,6-triene derivatives 10d and 16 (Scheme 3 and 5, respectively). It seems that in some cases the well known thermally disrotative valence isomerization of cyclononatetraenes 7 to 3a, 7a-dihydroindenes 8 is much slower than the formation of bicyclo[6.1.0]nona-2,4,6-trienes of the type 10 and 16 . This type of reaction hurts the Woodward-Hoffmann rules. Possible precursors of the attractive nonaheptafulvalene are prepared by reaction of acetoxy-tropylium fluoborate ( 19a ) as well as of bromo-tropylium bromide ( 19b ) with lithium-cyclononatetraenide (Scheme 8). So far, the attempted gas-phase pyrolysis of the precursors 21a and 21b failed to give nonaheptafulvalene (5).     

Notiz über die Synthese von Iso-, Noriso- und Desäthyl-tuboflavin

Treatment of 4,5 -dihydrocanthin-6-one (V) (prepared from synthetic canthinone (IV)) with ethyl or methyl magnesium iodide and methanolic hydrochloric acid yielded the ethyl or methyl compounds VI and IX. Oxidation of the latter compounds with selenium dioxide in dimethylformamide gave rise to the Pleiocarpa alkaloids isotuboflavine (II) and norisotuboflavine (III) in low yields. Deethyltuboflavine (VIII) was isolated as a byproduct from further oxidation of norisotuboflavine.     

Beitrag zur Analytik und Synthese von 3-Hydroxy-4-oxocarotinoiden

Contribution to the Analytical Separation and the Synthesis of 3-Hydroxy-4-oxocarotenoids (3RS,3′RS)-Astaxanthin (= 3,3′-dihydroxy-β,β-carotene-4,4′-dione, 1:1-mixture of racemate and meso-form; 1 ) can be separated into its optical isomers (3S,3′S)- 1a , (3R,3′R)- 1b and meso-(3R,3′S)- 1c via the corresponding diastereomeric di-(?)-camphanates. Some aspects of the configurational stability of astaxanthin are discussed. - HPLC. analysis of the (?)-camphanates of 3-hydroxy-4-oxocarotenoids provides, in suitable cases and supported by spectroscopic data, an analytical method for the simultaneous determination of constitution and chirality.     

Isomerisierung von Methoxy- und Carbomethoxysubstituierten Cycloalkyl- und Alken-radikalkationen

The very complex isomerization patterns of methoxy and carbomethoxy substituted cycloalkanes (3- to 7-membered rings) have been investigated using collisional activation, metastable ion characteristics and field ionization kinetics. The extent of isomerization depends on both the ring size and the substituent. Irrespective of the electronic properties of the substituent, ring opening involves exclusively the C-1? C-2 bond whereby linear alkene radical cations are formed. In the case of OCH₃- and COOCH₃ substituents the position of the resulting double bond (terminal or α,β-unsaturated) is determined more by the ring size of the precursor molecules and less by the electronic properties of the substituents. Contrary to these findings alklyl substituted cycloalkanes (3- to 5-membered rings) rearrange exclusively to terminal alkene radical cations. The barrier for double bond isomerization seems to be substantially influenced by substituents.     

Eine neue Methode zur Identifizierung von Alkyl- und Arylgruppen organischer Sulfide

Ohne Zusammenfassung     

Notiz zur polarographischen Bestimmung von Nickelspuren in Kobalt und Reinstkobaltsalzen

Zusammenfassung Die Stabilitätskonstante des Molybdän(V)-oxinatkomplexes wurde spektralphotometrisch und durch Austauschmessungen zu K=1,39 · 10^–12 ± 0,02 bestimmt. Beide Verfahren zeigen eine sehr gute Übereinstimmung. Der Komplex ist in 50%igem Aceton-Wasser über 3 Std stabil und kann analytisch zur Spurenbestimmung nach der Methode von Busev u. Fan verwendet werden.

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Summary The stability constant of Mo₂O₃(C₉H₆NO)₄ was determined spectrophotometrically and by displacement reactions as K=1.39 · 10^–12 ± 0.02. Both methods gave the same results. The complex is stable over three hours in 50% acetone and at pH 4.0 and can be employed for the determination of traces of molybdenum by the method of Busev and Fan.

     

Notiz zur Darstellung von o-Diacetylbenzol

Detailed directions for the preparation in large amounts of o-diacetylbenzene (I) and the intermediate products 1-methyl-4-chlormethylnaphthalene and 1.4-dimethylnaphthalene are given.     

Notiz zur elektronenstoßinduzierten Ringkontraktion von Cycloalkanonen und zur Struktur der -Ionen

Collisional activation demonstrates that the cyclooctanone cation does not isomerize to ionized 2-ethylcyclohexanone prior to ethylene elimination. In addition evidence is presented that the structures of the m/e 98 ions formed by single and by double McLafferty rearrangement in some cycloalkanones differ according to the structure of their precursors.