Selektive katalytische Hydrierungen und Hydrogenolysen, 5. Mitt. Ein einfacher Zugang zu 1-Benzyl-5,6,7,8-tetrahydroisochinolinen

Selective Catalytic Hydrogenations and Hydrogenolyses, V: Convenient Preparation of 1-Benzyl-5,6,7,8-tetrahydroisoquinolines 1-Benzylisoquinolines 1 can be hydrogenated selectively with Pt and Ru catalysts to yield the title compounds 2 . Using Pd/charcoal, the products 2 contain ca. 5% of the isomers 3 , which can be separated via the N-acetyl derivatives, e. g. 7d . Extended reaction times in the presence of platinum cause simultaneous hydrogenation of the unsubstituted aromatic nucleus of the benzyl group. At higher temperatures, the substituted benzyl nucleus is hydrogenated, too, involving C,O-hydrogenolysis, e. g. 1a → 4 or 1d → 4 . The structures of 2 were proved by ¹H-NMR spectroscopy. Compound 2a was prepared independently from 2c via 5 → 6 .     

Dihydroisochinolinumlagerung, 27. Mitt. Ein neuer Vorschlag zum Mechanismus

Dihydroisoquinoline Rearrangement, XXVII: Proposal of a New Mechanism For the mechanism of the rearrangement of 1-benzyl-1,2-dihydroisoquinolines a new proposal is presented, which is compatible with all presently known facts. The elimination, which was formerly regarded as a side reaction, is now considered to be the starting reaction. The rearrangement is assumed to proceed via ion pairs as an S_N2′-reaction. The first step of this mechanism was confirmed by experiments.     

Ein einfacher Zugang zu Derivaten des 5-Hydroxy-2-piperidons,Synthese eines homologen Hydroxypiracetams

Facile Access to 5-Hydroxy-2-piperidone Derivatives. Synthesis of a Homologous Hydroxypiracetam A three-step reaction is described that yields 5-hydroxy-2-piperidon (6). Using this facile access to 6 and its derivatives, the homologue 10 of hydroxypiracetam (2b) is prepared. Deprotection of the TBDMS ether 9 was achieved by hydrogenolysis over Pd on charcoal, which for hydrophilic compounds is more convenient than the fluoride method.     

Ein Zugang zu enantiomerenreinen DAVA-Derivaten, 2. Mitt.6): Synthese homochiraler 2-Piperidone aus D-Ribonolacton

Approach to Enantiomerically Pure DAVA-Derivatives, II: Synthesis of Homochiral 2-Piperidones from D-Ribonolactone Catalytic hydrogenation of the azide 8 , prepared from D-ribonolactone, furnishes the 2-piperidone 9 . Modification of the functional groups provides the homochiral 5-hydroxy-Δ³ piperidine-2-ones 20 and 21 . Hydrolytic ring cleavage of 20 does not furnish 23 . Treatment of 19 with barium hydroxide affords the benzylenolether 22 with isomerization of the double bond. Hydrolysis of 14 gives 5-amino-2R,3R,4R-trihydroxy-pentanoic acid 18 .     

Acetylenchemie, 5. Mitt. PTC-Umsetzung von 4-Hydroxychinolin-2-on und Indolin-2-on mit 3-Bromprop-1-in

Acetylenic Chemistry, Part 5.: PTC Reaction of 4-Hydroxyquinolin-2-one and Indolin-2-one with 3-Bromoprop-1-yne PTC propynylations of the titel compounds yield an oxazoloquinolinone and five propynylquinolinones; furthermore, three propynylindolinones and a propynylanthranilic acid ester were obtained. Possible reaction pathways are discussed. The results are compared with those reported earlier.     

Beiträge zur Chemie des Pyrazolsystems, 1. Mitt.: Ein effizienter Zugang zu Aryl- oder Benzyl-4-pyrazolylketonen und -carbinolen

Pyrazole Chemistry I: Efficient Syntheses of Aryl or Benzyl 4-Pyrazolyl Ketones and Carbinols Dilithiation of 4-bromopyrazole followed by reaction with appropriate electrophiles provides an improved access to 4-benzoylpyrazole ( 3 ) and the corresponding alcohol 4a. In a similar manner the homologous compounds 5 and 7 are conveniently available.     

Intramolekulare Aromatenalkylierungen, 22. Mitt. Synthese von cis-1,6,10-Trimethyl-1,2,3,4,5,6,7,8,9,10-decahydroindolo(4,3-fg)chinolin,ein neuer Zugang zum Ergolin-Gerüst

Intramolecular Alkylations of Aromatic Compounds, XXII: Synthesis of cis-1,6,10-Trimethyl-1,2,3,4,5,6,7,8,9,10-decahydroindolo(4,3-fg)quinoline, a New Approach to the Ergolen Framework The carbinols 7 , readily available from indole carboxaldehydes 5 and bromopicoline 6 , are hydrogenolized directly or via the ethers 8 to give the lutidinylindoles 9 . The isomeric ketone 17 can be prepared only from the mixed anhydride 15 , but not from nitrile 14 , by Grignard reaction with 16 . The bases 9 are converted to the quaternary salts 10 and reduced by NaBH₄ to yield the tetrahydrolutidinyl derivatives 11 , which fail to undergo cyclisation to 12 . After reduction of 11 to the diastereomeric mixture of indolines 13, 13a can be cyclised for the first time to give the ergolen derivative 2 .     

Heterocyclen via Mannich-Kondensation, 6. Mitt. Synthese von 2-Amino-3-pyridyl-phenylketonen

Heterocycles via Mannich Condensation, VI: Syntheses of 2-Amino-3-pyridylphenyl Ketones The ethyl 2-benzoylacetimidates 1a-c and 2-benzoylacetamidine (2a) exist in solution as enols. Ketonic Mannich bases condense with 1a-c and 2a to yield 2-amino-3-pyridylphenyl ketones.     

Heterocyclische Spirocyclohexadienone, 3. Mitt.

Heterocyclic Spirocyclohexadienones, III With N-methyl-naphthylamine 3-substituted 2-naphthol derivatives give the corresponding spirocyclohexadienones in good yields; 9-phenanthrol also proceeds analogously. 4-Substituted 1-naphthols react similarly but the spiroketones thus obtained are more labile and are formed in minor yields. From the behaviour of spirocyclohexadienones with protonic acids, carbonyl reagents and complex hydrides a reaction mechanism is deduced.     

Kondensierte Pyrane, 3. Mitt.

Condensed Pyranes, III Pyranopyrimidinecarboxylic esters can be prepared by reacting barbiturates, paraformaldehyde, and the esters of unsaturated carboxylic acids. Three pyranopyrimidinecarboxylic acids obtained by saponification were tested for antiphlogistic activity.     

Dihydroisochinolin-Umlagerung 12. Mitt.: Untersuchungen zum Geltungsbereich1)

Dihydroisoquinoline-Rearrangement The 1-cinnamyl-dihydroisoquinoline VII as a vinylogous 1-benzyl-compound is rearranged by diluted acids, the 1-styryl-dihydroisoquinoline VIII however disproportionates. The 1-allyl-compound XX gives the rearrangement product in a very high yield.     

Chinon-Amin-Reaktionen, 13. Mitt. Synthesen von Chinoxalinonen und Naphthochinoxalinon zum Farbvergleich mit Benzochinoxalinonen

Quinone-Amine Reactions, XIII: Syntheses of Quinoxalinones and Naphthoquinoxalinone for Colour Comparison with Benzoquinoxalinones Syntheses of the quinoxalinones 2/3 and of the naphthoquinoxalinone 4 are reported. Comparison of the electronic absorption spectra with those of the benzoquinoxalinones 1 indicates a hypsochromic shift of the absorption maximum of the quinoxalinone system by fusion. The same effect is observed on NH/S exchange in 3 yielding the benzothiazinone 6 .     

Cer(IV)oxidationen von β-Aminoketonen, 6. Mitt.: Untersuchungen zum Reaktionsverlauf

Cerium(IV) Oxidations of β-Aminoketones., VI: Investigations on the Reaction Mechanism Cerium(IV)sulfate oxidations of N-benzyl-4-piperidones are characterized by a radical mechanism: the cyclisation product, the methanobenzazocine 2 , is formed via a C-3 intermediate, the dehydrogenation products 3 and 4 are obtained from peroxyradicals.     

Chirale 3-Aminopropanole, 2. Mitt. N-Alkylierungsprodukte

Chiral 3-Aminopropanols, II: N-Alkylated Products From the racem. and optically active 3-aminopropanols 1a-1d the N-monomethyl compounds 3 are obtained via the urethanes 2 . Methylation of 1a-1d according to Eschweiler-Clarke or reaction with formaldehyde/NaBH₃CN yield the N-dimethyl compounds 4 . With acetone/NaBH₄ 1a-1d react to give the N-isopropyl compounds 6 .     

Die Cyanessigesterreaktion substituierter Naphthochinone. 2. Mitt.: Beitrag zum Reaktionsmechanismus

Cyanoacetate Reaction of Substituted Naphthoquinones. Part II The reaction between 2-methyl-1,4-naphthoquinone and cyanoacetate has been studied. The structure model of the sodium hydrogen sulfite derivative permits an insight into the mechanism of the reaction. NMR-spectrometry brings direct evidence for the bonding on the quinoidal skeletal structure. In accordance with the analogous model a 1,2-addition can be assumed. The reaction is base catalysed. An attack by the carbanion of cyanoacetate on C-2 of the quinoidal system takes place.     

Ein neuer Typ von analgetischen Antiphlogistica, 2. Mitt. Benzo[b]thienyl-piperazine

A Novel Type of Analgesic Antiphlogistics, II: Benzo[b]thienyl-piperazines In continuation of our work on antiphlogistic benzo[b]thiophene 1,1-dioxides novel compounds of type I were synthesized by the addition of piperazine(s) onto 2-phenylbenzo[b]thiophene 1,1-dioxides and (in some cases) by subsequent substitutions. Utilizing the reversibility of the addition reaction, the basic substituent at position 3 of such compounds can be replaced by other groups.     

Reaktionen mit Aziridinen, 17. Mitt. Notiz zum Pyrrolidon-Ringschluß bei der Amidoethylierung von Malonester

Reactions with Aziridines, XVII:²⁾ Note Concerning the Formation of Pyrrolidone by Amidoethylation of Malonic Ester Whilst amidoethylation of di-tert. butyl malonate with 1-(cyclohexylcarbamoyl)aziridine ( 1a ) leads to the 1,3-diacylpyrrolidone 5a only, the analogous reaction with 1-(tert. butylcarbamoyl)-aziridine ( 1b ) yields a mixture of the 1,3-diacylpyrrolidone 5b and the primary amidoethyl derivative 3b .     

Trichomonazide Wirkstoffe, 3. Mitt. Aryloxy-chlor-1,3,5-triazine

Trichomonacidal Agents, III: Aryloxy chloro- 1,3,5-triazines The reaction of 2,4-dichloro-6-(dihexylamino)-1,3,5-triazine (1) with the phenols 2 leads at low temperatures to the monoaryloxy(chloro)-1,3,5-triazines 3a–c and under more drastic conditions to the bis(aryloxy)-1,3,5-triazines 4c–d . A characteristic of these new compounds is the cleavage of the aryloxy groups on electron impact as examplified by the transition of 4c from m/z = 504 to m h = 383. Marked trichomonacidal and antidiabetic activities are exhibited especially by 3b .