A general intramolecular Diels–Alder approach to tricyclic sesquiterpenes: stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene

1987 ◽  
Vol 65 (1) ◽  
pp. 114-123 ◽  
Author(s):  
Kazimierz Antczak ◽  
John F. Kingston ◽  
Alex G. Fallis ◽  
Alfred W. Hanson
Keyword(s):  
Double Bond ◽  
Methyl Ester ◽  
Ring System ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
Total Syntheses ◽  
Methyl Group ◽  
X Ray ◽  
12 Steps ◽  
Selective Hydrogenolysis

Stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene are described. The sequence employs a "blocked" cyclopentadiene in which the cyclopropane unit also serves as a latent methyl group. Thus intramolecular [4 + 2] cycloaddition of the substituted methyl spiro[2.4]hepta-4,6-dien-1-yl-2-pentenoate 13c affords 5-benzyloxy-6-isopropyl-8-carbomethoxytetracyclo[5.4.01,7.02,4.02,9]undec-10-ene (14c), which after selective hydrogenolysis generates the tricyclo[4.4.01,6.02,8]decane (sinularene) ring system. Removal of the secondary hydroxyl function by elimination and hydrogenation (Ph3P/CCl4/CH3CN; H2/Pd/C), reduction of the methyl ester (LiAlH4), and introduction of the exocyclic double bond (acetate pyrolysis, 550 °C) completes the synthesis of (±)-sinularene in 12 steps from aldehyde 7. A parallel series of reactions employing the isopropyl triene epimer 13a affords (±)-5-epi-sinularene. X-ray analyses of the triene 13a and the adduct 14a are also reported.

scholarly journals Stereoselective total syntheses of (±)-sinularene and (±)-5-epi-sinularene: a general intramolecular Diels–Alder approach to tricyclic sesquiterpenes

1985 ◽  
Vol 63 (4) ◽  
pp. 993-995 ◽  
Author(s):  
Kazimierz Antczak ◽  
John F. Kingston ◽  
Alex G. Fallis
Keyword(s):  
Double Bond ◽  
Methyl Ester ◽  
Total Synthesis ◽  
Ring System ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
Total Syntheses ◽  
Methyl Group ◽  
Secondary Hydroxyl ◽  
Selective Hydrogenolysis

Stereoselective total synthesis of (±)-sinularene and (±)-5-epi-sinularene are described. The sequence employs a "blocked" cyclopentadiene in which the cyclopropane unit also serves as a latent methyl group. Thus intramolecular [4 + 2] cycloaddition of the substituted methyl spiro[2.4]hepta-4,6-dien-1-yl)-2-pentenoate 11 affords 5-benzyloxy-6-isopropyl-8-carbomethoxytetracyclo[5.4.01,7.02,4.02,9]undec-10-ene (12) which after selective hydrogenolysis generates the tricyclo[4.4.01,6.02,8]decane (sinularene) ring system. Removal of the secondary hydroxyl function (Ph3P/CCl4/CH3CN; H2/Pd/C), reduction of the methyl ester (LiAlH4), and introduction of the exocyclic double bond (acetate pyrolysis, 550 °C) completes the synthesis of (±)-sinularene in 14 steps from cyclopentadiene. A parallel series of reactions employing the isopropyl epimer of 12 affords (±)-5-epi-sinularene.

Diels-Alder dimerization of a hexenylidene-substituted Benzofuran-2(3H)-one

1983 ◽  
Vol 36 (2) ◽  
pp. 389 ◽  
Author(s):  
H Becker ◽  
SR Hall ◽  
BW Skelton ◽  
AH White
Keyword(s):  
Double Bond ◽  
Single Crystal ◽  
Structure Determination ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
X Ray ◽  
Aromatic Systems ◽  
Aromatic Hydrogen

(Z)-7-t-Butyl-5 methoxy-3-[(Z)-2?-methoxy-5,5'-dimethyl-4'-oxohex-2'-enylidene]benzofuran-2(3H)-one has been found to undergo Diels-Alder dimerization in which the exocyclic double bond adds to the s-cis diene moiety. The stereochemistry of the Diels-Alder dimer was established by a single-crystal X-ray structure determination. Crystals of the dimer, C44H56O10, are monoclinic, P21/n, a 12.23(1), b 19.43(2), c 18.71(2) �, β 107.76(7)�, Z 4; a residual of 0.046 was obtained for the 2519 'observed' reflections. In the dimer, two benzofuranone moieties are situated so as to be vicinal spiro substituents of the cyclohexene formed in the Diels-Alder addition. The bond between the two benzofuranone units is unusually long [1.597(6)�]. The shielding of one aromatic hydrogen in the n.m.r. spectrum of the dimer results from the disposition of the two aromatic systems.

The Structure of Polyisoprenes. II. The Structure of β-Gutta-Percha

1945 ◽  
Vol 18 (2) ◽  
pp. 280-283
Author(s):  
G. A. Jeffrey
Keyword(s):  
Molecular Structure ◽  
Double Bond ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
Interatomic Distances ◽  
Methyl Group ◽  
X Ray ◽  
Gutta Percha ◽  
Qualitative Estimate

Abstract The x-ray diffraction data at present available from β-gutta-percha are shown to be insufficient to distinguish fine details of molecular structure. Since a qualitative estimate of the intensities on the fibre diagram can be adequately satisfied by a model having normal interatomic distances and valency angles, no evidence exists for the improbable distortion of the methyl group out of the plane of the double bond previously ascribed to the molecule.

BEZIEHUNGEN ZWISCHEN SUBSTITUTION IM RING A UND ABBAU IM STOFFWECHSEL BEI VERWANDTEN DES TESTOSTERONS

1962 ◽  
Vol 41 (4) ◽  
pp. 494-506 ◽  
Author(s):  
H. Langecker
Keyword(s):  
Double Bond ◽  
Ring System ◽  
Keto Group ◽  
Hydroxyl Group ◽  
Methyl Group ◽  
Structural Peculiarities ◽  
Metabolic Degradation ◽  
The Difference ◽  
Testosterone Metabolites ◽  
Derivatives Of

ABSTRACT Judging from the metabolites found in the urine, 1-methyl-androst-1-en-17β-ol-3-one (methenolone) and testosterone are metabolized in a different manner. For further clarification, other derivatives of testosterone with modifications in Ring A were investigated with regard to the oxidation of the 17-hydroxyl group. The production of urinary 17-ketosteroids decreased in the following sequence: testosterone; 1α-methyltestosterone and androstan-17β-ol-3-one; 1β-methyl-androstan-17β-ol-3-one; 2α-methyl-androstan-17β-ol-3-one and androst-1-en-17β-ol-3-one; 1α-methyl-androstan-17β-ol-3-one; 1-methyl-androsta-1,4-dien-17β-ol-3-one; 1,17α-dimethyl-androst-1-en-17β-ol-3-one and 1 -methyl-androst-1 -en-17β-ol-3-one (methenolone). The difference in metabolic degradation is also demonstrated in the fractionation of the urinary ketones. While after the administration of testosterone practically only hydrogenated 17-ketones are observed in the urine, the unchanged compound is still traceable in remarkable quantities after the administration of methenolone, along with minor quantities of the corresponding diketone. Testosterone-metabolites here are absent, whereas they represent the major substances present after the administration of androst-1-en-17β-ol-3-on. Following the administration of 1α-methyltestosterone only hydrogenated 17-ketones are detected which are still partly methylated. The 1-methyl-group and the Δ 1-double-bond seem to be responsible for the inhibition of the oxidation of methenolone in the 17-position. In addition, the hydrogenation of the double-bond and the reduction of the 3-keto-group are inhibited, obviously on account of the same structural peculiarities. The demethylation of methenolone is also inhibited. Any change in the steroid ring system forms a new substrate, thus producing new conditions for the enzymatic attack in the metabolic degradation.

The Structure of Polyisoprenes. IV. Double-Bond Interaction in Certain Carbalkoxy-Substituted 1,5-Dienes

1946 ◽  
Vol 19 (1) ◽  
pp. 14-22
Author(s):  
L. Bateman ◽  
G. A. Jeffrey
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Methyl Ester ◽  
X Ray ◽  
Bond Interaction ◽  
Carbon Framework ◽  
New Interpretation ◽  
Related Compounds ◽  
Ray Methods ◽  
Crystallization From Solution

Abstract A peculiar lack of olefinic reactivity, combined with a facility for cyclization of methyl and ethyl Δ1,5-hexadiene-1, 1, 3, 3, 4, 4, 6, 6-octacarboxylates, has been attributed by Ingold, Parekh, and Shoppee to ring-chain mesomerism. A reinvestigation of these and related compounds has now been made by using x-ray methods, and it is shown that the crystal structure of the methyl ester is incompatible with the cis-configuration required for such interspatial double-bond saturation. A radical disruption of a mesomeric system by crystallization from solution is improbable and, an earlier formulation incorporating a bicyclobutane nucleus being rejected on chemical grounds, it is necessary to seek a new interpretation of the anomalous reactivity. We suggest that the determinative condition is hyperconjugation throughout the carbon framework of the molecule, and discuss this in relation to 1,5-dienes generally.

A Direct Synthesis of a Strongly Zwitterionic 6,6'-Diaminofulvalene

2014 ◽  
Vol 69 (5) ◽  
pp. 580-588 ◽  
Author(s):  
Dominic Schmid ◽  
Alexander Seyboldt ◽  
Doris Kunz
Keyword(s):  
Double Bond ◽  
Theoretical Analysis ◽  
Dft Calculations ◽  
Structure Analysis ◽  
Direct Synthesis ◽  
Exocyclic Double Bond ◽  
X Ray ◽  
One Step ◽  
Initial Route ◽  
Guanidinium Salt

Upon reaction of the dipyrido-anellated guanidinium salt 1 with one equivalent of CpNa we were able to synthesize the dipyrido-anellated diaminofulvalene 4 in one step in 33% isolated yield. This shortens the initial route that applies a literature-known fulvalene synthesis via uronium salt 3 by two steps and avoids the need for a sacrificial equivalent of CpNa. Although the X-ray structure analysis reveals a shorter exocyclic double bond than observed in the diaminofulvalene V, a theoretical analysis based upon DFT calculations shows a stronger zwitterionic character for the dipyridofulvalene 4.

pKa values of protonated α,β-unsaturated cyclic carboxylic acids. Effect of ring size on acidities

1978 ◽  
Vol 56 (15) ◽  
pp. 2003-2007 ◽  
Author(s):  
S. N. Bhat ◽  
Rama Rao ◽  
K. Ranganayakulu
Keyword(s):  
Double Bond ◽  
Carboxylic Acids ◽  
Acid Strength ◽  
Ring System ◽  
Ring Size ◽  
Methyl Group ◽  
Tiglic Acid ◽  
Conjugate Acid ◽  
The Difference ◽  
Steric Inhibition Of Resonance

The pKa values of protonated α,β-unsaturated acids, namely tiglic, cyclopentene carboxylic, cyclohexene carboxylic, and cycloheptene carboxylic acids have been determined spectrophotometrically and the values are −4.08, −4.05, −3.88, and −3.84, respectively. The conjugate acid of tiglic acid is a stronger acid than that of crotonic acid (pKa − 3.94) and the difference in acid strength is explained on the basis of steric inhibition of resonance by the α-methyl group. All the protonated cyclic acids are shown to be somewhat weaker than the corresponding acyclic ones. Several factors have been considered to explain the acid strength of these cyclic α,β-unsaturated acids. It has been shown that the ease of placing the double bond exo to the ring system is responsible for the changes in acidity of the above cyclic systems.

Die Molekülstruktur eines neuen [3 + 1]-Cycloadditionsproduktes · Röntgenstrukturanalyse von 3-Cyclohexylimino-2-(p-fluorphenyl)-4.4-bis(trifluormethyl)-1-azetin / Molecular Structure of a New [3 + 1]-Cycloaddition Product. X-Ray Structure Analysis of 3-Cyclohexylimino-2-(p-fluorophenyl)-4,4-bis-(trifluoromethyl)-1-azetine

1974 ◽  
Vol 29 (5-6) ◽  
pp. 399-402 ◽  
Author(s):  
Alfred Gieren ◽  
Klaus Burger ◽  
Willy Thenn
Keyword(s):  
Molecular Structure ◽  
Double Bond ◽  
Structure Analysis ◽  
Exocyclic Double Bond ◽  
X Ray ◽  
Bond Lengths ◽  
Structural Relationships ◽  
Cycloaddition Product ◽  
Bonding Systems

The structure of a [3 + 1]-cycloaddition product of a nitrile ylide - obtained from a 4,5-dihydro-1,3,5-oxazaphosph(V)ole - and cyclohexylisonitrile was determined by X-ray structure analysis. The constitution of this molecule, which was proposed by way of spectroscopic datas, could be verified and the configuration at the exocyclic double bond was elucidated. Details of the conformation are discussed. Bond distances and angles are compared with other molecules, which contain very similar bonding systems, but in different structural relationships. The four-membered azetine ring is strained. The bond lengths of the endoand exocyclic C = N double bond of the 1.4-diaza-1.3t-butadiene system are significantly different.

scholarly journals Cycloadditionen, XX Thermisch induzierte intramolekulare Reaktionen bei 2-Methyl-2,3-butadienamiden / Cycloadditions, XX Thermally Induced Intramolecular Reactions of 2-Methyl-2,3-butadienamides

1992 ◽  
Vol 47 (12) ◽  
pp. 1785-1794 ◽  
Author(s):  
Gerhard Himbert ◽  
Hans-Jürgen Schlindwein
Keyword(s):  
Double Bond ◽  
Alder Reaction ◽  
Diels Alder ◽  
Secondary Amines ◽  
Thermally Induced ◽  
Methyl Group ◽  
Diels Alder Reaction ◽  
Intramolecular Reactions ◽  
Derivatives Of ◽  
Allenic Acid

The 2-methyl-2,3-butadienamides 4a—m are directly synthesized by the reaction of the corresponding allenic acid chloride 2 with the secondary amines 3. At heating, 4a—j undergo the intramolecular Diels-Alder reaction, by using their ω-standing double bond and the π-system of the directly bonded phenyl groups or of the “methylenic” bonded arenes or furans. Thereby the tricycles 6a—g (bearing five-membered lactam moreties) and/or the tricycles 7-9 (bearing six-membered lactam moreties) are formed. The influence of the geminai methyl group on the chemoselectivity and on the velocity of the IMDA reactions is investigated. The N-allyl derivatives of 4 (s. 41 and m) form the bicycles 10 by intramolecular [2+2]-Cycloaddition.

Conformation of 1-Oxy Cyclohexenes Deriving from Diels-Alder Cycloaddition: Spectroscopic and X-Ray Crystal Structure Analysis

2000 ◽  
Vol 53 (3) ◽  
pp. 167
Author(s):  
Donald W. Cameron ◽  
Robert W. Gable ◽  
Ross M. Heisey ◽  
Jonathan M. White
Keyword(s):  
Crystal Structure ◽  
Double Bond ◽  
Structure Analysis ◽  
Chair Conformation ◽  
Crystal Structure Analysis ◽  
Diels Alder ◽  
X Ray ◽  
Cyclohexene Ring

For cycloadduct (6), derived by reaction of the (Z)-oxy diene (7) with the dienophile (8), the newly formed cyclohexene ring is shown by spectroscopic and X-ray crystal structure analysis to be based on the half-chair conformation (9). This contrasts with analogous diastereomeric adducts from (E)-oxy dienes, which are based on the ring-flipped conformation (4). The determinant for this conformational difference is suggested to be the stereoelectronic preference of the allylic oxy substituent, in (4) and (9), for a pseudoaxial orientation to the double bond of the cyclohexene system.

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