Showing papers on "Bicyclic molecule published in 1980"

Bicyclic and tricyclic ergoline partial structures. Rigid 3-(2-aminoethyl)pyrroles and 3- and 4-(2-aminoethyl)pyrazoles as dopamine agonists.

Abstract: It is proposed, based upon comparisons with apomorphine, that the rigid pyrroleethylamine moiety of the ergolines is the portion of the molecule responsible for dopamine agonist activity. In support of this hypothesis, bicyclic and tricyclic ergoline partial structures 6, 11, 25, and 35 have been synthesized. In addition, some pyrazole isosters (37, 38, 40, and 45) of these rigid pyrroleethylamines have been made. All of the classes show dopaminergic activity in prolactin inhibition and in lesioned rat turning assays. The most potent drugs, the linear tricyclic pyrazoles 38 (R = Pr) and 40 (R = Pr), are comparable in potency with the highly active ergoline pergolide (41).

The Physical Chemistry of 1,2-Dithiole Compounds-the Question of Aromaticity

Abstract: The parent compound, the 1,2-dithiolylium ion, can by successive addition of vinylenethio groups give rise to higher polycyclic systems each composed of 1,2-dithiole rings with the sulfur atoms in a row. Until now, however, it has only been possible to extend the system to compounds with 3 (l,6,6aλ4-tri-thiapentalene), 4 and 5 sulfur atoms in a row. The discussion of the structure of these systems has been based on results obtained by use of X-ray crystallography, electron diffraction, 1H NMR-, 13C NMR-, ESR-, Infrared-, microwave-, ESCA-, photo-electron spectroscopy and mass spectrometry. The results from other physico-chemical studies such as photo- and electrochemical studies have also been used in the discussion of bonding and structure. Physico-chemical data from the period 1970-1979 are included. Based on these physico-chemical studies the l,2, dithiolylium system seems to be an aromatic 6-φ-electron system. l,6,6aλ4-trithiapentalenes in all respects behave as bicyclic aromatic loλ-electron...

Synthese symmetrisch substituierter bicyclischer Guanidine

Abstract: Die symmetrisch 2,2,8,8-tetraalkylsubstituierten Guanidine 14a und b werden regioselektiv durch Aufbau der offenkettigen Triamine 11a und b und nachfolgende Cyclisierung dargestellt. Das unsubstituierte Guanidin 14c wird in guten Ausbeuten durch eine Eintopfreaktion erhalten. Synthesis of Symmetrically Substituted Bicyclic Guanidines The symmetrically 2,2,8,8-tetraalkylsubstituted bicyclic guanidines 14a and b are prepared stereoselectively via construction of the open-chain triamines 11a and b and subsequent cyclisation. A one-pot reaction gives the unsubstituted guanidine 14c in high yield.

A total synthesis of (±)-stemarin, a diterpenoid with a unique bicyclic C/D ring System

Abstract: A total synthesis of (±)-stemarin, a diterpenoid with a unique C/D ring System, is described. The synthesis features photoaddition of allene to an α,β-unsaturated ketone and two skeletal rearrangements. Application of the synthetic strategy described herein to a synthesis of stemodinol and aphidicolin is anticipated.

Stereochemistry of Four-coordinate Chelate Compounds of Schiff Bases and Their Analogues

Abstract: The problem of the configuration of the chelate group and the metal ring in chelates of transition metals with Schiff bases and their analogues is discussed, and the influence of various factors analysed, in particular the nature of the central metal atom and the steric and electronic effects of the ligands Various types of conformational changes in conjugated metal rings in bicyclic and tricyclic chelates are surveyed, and factors influencing these changes are noted The conformation of the non-conjugated metal rings in tricyclic chelates is discussed A list of 188 references is included

Bicyclic heterocycles with nitrogen at the ring junction. Part 2. Application of the Dakin–West reaction to the synthesis of imidazo[5,1-f]-1,2,4-triazin-4(3H)-ones

Abstract: A series of novel acylamino α-keto-esters (4) have been prepared via a Dakin–West reaction of acylated a-aminoacids and ethyl oxalyl chloride. Their use in a general synthesis of imidazo[5,1-f]-1,2,4-triazin-4(3H)-ones (7) is described. The conversion of the imidazotriazinones into the corresponding imidazo[5,1-f]-1,2,4-triazines (20) and their 3,4-dihydro-derivatives (19) are also reported.

Mechanistic studies in the chemistry of urea. Part 4. Reactions of urea, 1-methylurea, and 1,3-dimethylurea with benzil in acid solution

Abstract: In acid solution benzil reacts with urea and with 1-methylurea to give the bicyclic products (2) and (3b) and with 1,3-dimethylurea to give 1,3-dimethyl-5,5-diphenylhydantoin (5). The initial step in the reaction is attack by urea on protonated benzil to give the diol (6). Further reaction of (6) is governed by its tendency to eliminate water.

Stereoelectronic control in acetal formation

Abstract: The cyclization under acidic conditions of bicyclic and monocyclic hydroxypropyl methoxytetrahydropyrans 1 and 4 is reported. At room temperature, compound 1 gives only cis tricyclic acetal 2. At r...

Comparison of biological effects of N-alkylated congeners of beta-phenethylamine derived from 2-aminotetralin, 2-aminoindan, and 6-aminobenzocycloheptene.

Abstract: Three series of bicyclic, semirigid congeners of beta-phenethylamine have been prepared for evaluation of the effect of ring size (and of concomitant conformational variation) on biological activity in a variety of assays for adrenergic and dopaminergic actions. Pharmacologic activity was associated with 2-aminotetralin and 2-aminoindan derivateves, but was not found with 6-aminobenzocycloheptene derivatives. Noteworthy is the ability of several aminotetralins and aminoindans to increase the hot-plate reaction time without eliciting dopaminergic effects. This action was not blocked by pretreatment with naloxone.

Struktur eines O, N-Ketenacetals: (1 RS, 8 SR, 10 SR, 4(15)Z)-4-äthyliden-5-oxa-3-azatricyclo [8.4.0.03,8]tetradecan†

Abstract: Structure of a O,N-Keteneacetal: (1RS, 8SR, 10SR, 4(15)Z)-4-Ethylidene-5-oxa-3-azatricyclo [8.4.0.03,8]tetradecane1 Methods for the preparation of a series of model compounds which were required for stereochemical studies are described: the tricyclic O, N-keteneacetal 1, the two diastereomeric bicyclic amino acids 7 and 10 (see Scheme 2), and the two diastereomeric conformationally fixed tetrahydro-1,3-oxazines (=1,3-oxazixanes) 9 and 11. An x-ray analysis of racemic 1 reveals a quasi-tetrahedral nitrogen pyramid of the O, N-ketene acetal grouping, and an almost perfect conformational analogy between the N- and C-centered allylic positions at the double bond.

Cycloadditions of Allyl Cations, 21. Synthesis and 1H NMR Spectra of Bicyclo[3.2.1]octa‐2,6‐Dienes and 3‐Methylenebicyclo[3.2.1]oct‐6‐enes from Bicyclo[3.2.1]oct‐6‐en‐3‐ones Methylated at C‐2 and C‐4

Abstract: Bicyclo[3.2.1]oct-6-en-3-ones 5–8, methylated at C-2 and C-4, have been transformed into methylated bicyclo[3.2.1]octa-2,6-dienes 19–24 and 3-methylenebicyclo[3.2.1]oct-6-enes 16–18 by three routes: 1) Conversion into tertiary alcohols 9–11 with methylmagnesium halide and dehydration. 2) Reduction to epimeric secondary alcohols 12–15 with LiAlH4 and also i-Bu2AlH, followed by dehydration. 3) Methylenation with CH2Br2, Zn/TiCl4 in THF/CH2Cl2. — The reduction of 2,4-methylated bicyclo[3.2.1]oct-6-en-3-ones 5–8 with LiAlH4 and i-Bu2AlH gives axial and equatorial alcohols; the sterically more demanding i-Bu2AlH attacks preferentially from the exo side, yielding predominantly axial alcohols. Physical, spectroscopic, and chemical properties of the resulting bicyclo[3.2.1]oct-6-en-3-ols 12–15 have been correlated by conformational analysis. Axial alcohols form hydrogen bonds intramolecularly, giving inter al. lower melting points and shorter retention times than equatorial alcohols, a sharp OH band in the IR, and a downfield 1H NMR shift of the signals of the olefinic protons 6-H, 7-H (in CCl4 solvent). They also show marked coupling (3J = 10–12 Hz) of the OH proton in solvent CCl4. Exceptions to these trends are ascribed to flattening of the six-membered ring. The dehydration of the sterically hindered tertiary 3-methylbicyclo[3.2.1]oct-6-en-3-ols 9–11 with phosphoryl chloride in pyridine produces bicyclo[3.2.1]octa-2,6-dienes 19–21 in high yields, but requires forcing conditions (≈100°C) compared to secondary alcohols (0–25°C). Bicyclo[3.2.1]octa-2,6-dienes, unlike the isomeric 3-methylenebicyclo[3.2.1]oct-6-enes, form crystalline AgNO3 complexes. 2,3,4,4-Tetramethylbicyclo[3.2.1]octa-2,6-diene (21) reacts with atmospheric oxygen at ambient temperature and −20°C to give 2,4,5,5-tetramethyl-3-oxatricyclo[4.2.1.02,4]non-7-ene (26). Cycloadditionen von Allyl-Kationen, 21. Synthese und 1H-NMR-Spektren von Bicyclo[3.2.1]octa-2,6-dienen und 3-Methylenbicyclo[3.2.1]oct-6-enen aus 2,4-methylierten Bicyclo[3.2.1]oct-6-en-3-onen 2,4-Methylierte Bicyclo[3.2.1]oct-6-en-3-one 5–8 wurden auf drei Wegen in methylierte Bicyclo[3.2.1]octa-2,6-diene 19–24 und 3-Methylenbicyclo[3.2.1]oct-6-ene 16–18 umgewandelt: 1) Reaktion mit Methylmagnesiumhalogenid zum tertiaren Alkohol 9–11 und Dehydratation. 2) Reduktion zu den entsprechenden epimeren sekundaren Alkoholen 12–15 mit LiAlH4 und i-Bu2AlH und anschliesende Dehydratation. 3) Direkte Methylenierung mit CH2Br2, Zn/TiCl4 in THF/CH2Cl2. — Die Reduktion der 2,4-methylierten Bicyclo[3.2.1]oct-6-en-3-one 5–8 mit LiAlH4, und i-Bu2ALH liefert axiale und aquatoriale Alkohole; das sterisch anspruchsvollere i-Bu2AlH greift vorzugsweise von der exo-Seite an unter Bildung axialer Alkohole. Physikalische, spektroskopische und chemische Eigenschaften der resultierenden Bicyclo[3.2.l]oct-6-en-3-ole 12–15 werden uber die Konformationsanalyse korreliert. Axiale Alkohole gehen intramolekulare Wasserstoffbrucken ein und haben niedrigere Schmelzpunkte und kurzere Retentionszeiten als aquatoriale Alkohole, eine scharfe OH-Bande im IR und eine Tieffeldverschiebung der olefinischen Protonen 6-H, 7-H im 1H-NMR-Spektrum. Sie zeigen auserdem eine ausgepragte Kopplung (3J = 10–12 Hz) des OH-Protons im Losungsmittel CCl4. Ausnahmen gegenuber diesen Trends werden einer Abflachung des sechsgliedrigen Rings zugeschrieben. Die Dehydratation der sterisch gehinderten tertiaren 3-Methylbicyclo[3.2.l]oct-6-en-3-ole 9–11 mit Phosphoroxychlorid in Pyridin liefert Bicyclo[3.2.l]octa-2,6-diene 19–21 in hoher Ausbeute, aber benotigt forcierende Bedingungen (≈100°C) im Vergleich zu den sekundaren Alkoholen (0–25°C). Anders als 3-Methylenbicyclo[3.2.l]oct-6-ene bilden die gespannten isomeren Bicyclo[3.2.l]octa-2,6-diene kristalline AgNO3-Komplexe. 2,3,4,4-Tetramethylbicyclo[3.2.l]octa-2,6-dien (21) reagiert bei Raumtemperatur und −20°C mit atmospharischem Sauerstoff unter Bildung von 2,4,5,5-Tetramethyl-3-oxatricyclo[4.2.1.02,4]non-7-en (26).

Oil-soluble substituted mono and bicyclic oxazolidines, their preparation and use as additives for functional fluids

Abstract: Oil-soluble 4-alkyl mono or 5-alkyl bicyclic oxazolidines, e.g. 1-aza-3,7-dioxabicyclo[3.3.0] octanes which are the reaction products of an aldehyde and an amino propane monol or diol are additives which feature activity in functional fluids, e.g. mineral oil base automatic transmission fluids, as copper alloy corrosion inhibitors.