Exo Double Bond Research Articles

Enantioselective Synthesis and Conformational Analysis of Cyclohexene Carbocyclic Nucleosides

An enantioselective approach towards the synthesis of optically pure cyclohexene nucleosides 3 has been developed starting from (R)-carvone. The key steps are the regio- and stereoselective hydroboration of an exo double bond, the selective reduction of an enone intermediate and introduction of a base moiety by Mitsunobu reaction. Conformational analysis showed that the adenine base adopts predominantly in a pseudo-axial position.

Theoretical Study of the Q and B Bands of Free-Base, Magnesium, and Zinc Porphyrins, and Their Derivatives

The multireference Møller−Plesset perturbation (MRMP) theory with complete active space self-consistent field (CASSCF) reference functions is applied to the study of the Q and B bands of free-base, magnesium, and zinc porphyrins and their derivatives. The Q band of free-base porphyrin is so weak because the transition is pseudoparity-forbidden because of the alternancy symmetry. The Q band in the visible region can be intensified if the pairing property is broken. This is achieved by various chemical modifications to the basic structure of free-base porphyrin such as external substituents, changes in conjugation pathway, and change in central substituent. The intensity and color of the Q band as well as the macrocyclic porphyrin skeleton are perturbed to a greater or lesser extent by various chemical modifications. Insertion of aza groups in meso position leads to the shrinking of the size of the central hole, whereas hydrogenation to the exo double bond of pyrrole rings expands the central hole. Substitution of nitrogen atoms for meso carbon atoms significantly intensifies the oscillator strength of the higher energy side transition of the Q band with the peak position unchanged. Ring reduction widens the splitting of two peaks of the Q band, giving rise to the characteristically strong far-red band and the weaker visible band. Changes from metal-free to metalloporphyrins have a less dramatic effect on the spectra.

General stereoselective synthesis of ( E)- exo-alkylidene tetrahydrofurans via base-mediated cyclization of hydroxyl propargylic sulfones

The base-promoted cyclization of a number of phenyl propargylic sulfones possessing a β-hydroxyl group afforded 5-substituted ( E)-2-[(benzenesulfonyl)methylene]tetrahydrofurans 3 in >80% yield. The phenyl allenic sulfone, formed by isomerization of the phenyl propargylic sulfone under the basic conditions, is attacked by the internal alkoxide to give an allylic anion which undergoes protonation to form the conjugated exo double bond.

Photochemistry of ZnTPP induced by cadmium sulfide nanoparticles in 2-propanol

Addition of ZnTPP to non-stoichiometric CdS nanoparticles in 2-propanol leads to adsorption of ZnTPP molecules onto the surface of the nanoparticles. A limiting adsorption of about 13% ZnTPP molecules onto the surface of 2 × 10 −4 M CdS nanoparticles was determined by ultrafiltration (100 Å membrane filters). It corresponds to 6.15 × 10 −3 × m ZnTPP molecules adsorbed onto the surface of an average-size CdS nanoparticle; m is the number of CdS units in such a nanoparticles. Both the quenching of the recombination luminescence of CdS (e tr − / h tr +) by ZnTPP and the photoreactivity of ZnTTP in the presence of CdS nanoparticles are linked to the extent of adsorption of ZnTPP onto CdS. The adsorption of ZnTPP onto the surface of CdS nanoparticles is described by Langmuir-type plots. UV irradiation of ZnTPP in the presence of CdS nanoparticles leads to the formation of intermediate photoproducts, characterized with absorption bands in the red region of the spectrum, which subsequently convert to more stable photoproducts. The former photoproducts are attributed to reactions of O 2 − with ZnTPP whereas the latter may be linked to the reduction of ZnTPP, substitution at the exodouble bonds of ZnTPP and to open macrocyclic structures.

Three-component coupling polymerization of bisallene, aryl dihalides, and nucleophiles via ?-allylpalladium complex. II. Effect of nucleophiles on polymerization

A novel palladium-catalyzed three-component polycondensation of 1,2,10,11-dodecatetraene, 4,4′-diiodobiphenyl, and nucleophiles was carried out using various carbanions and amines as a nucleophilic part. The polymerization with various sodium diethyl malonates produced polymers in high yields. Particularly, no exo-double bond was detected in the polymers prepared from sodium diethyl malonates bearing substituents directly on the carbanion center. The ratios of E- and Z- isomeric units in the polymers were dependent on the structure of the nucleophiles used. Other carbanions with appropriate electron-withdrawing groups such as sulphones and ketones can be also used as a nucleophile for the present polycondensation. Within heteronucleophiles examined, cyclic amines were suitable to produce polymers in high yields. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1211–1218, 1997

Changes in chemical composition of catalytically hydrogenated orange oil ( Citrus sinensis)

Orange oil obtained from fresh fruit peels by cold pressing was subjected to hydrogenation at 60, 70 and 80°C and 0.46 MPa (H 2 pressure) over Adam's catalyst (PtO 2 at 0.5 and 0.75%, w/w). The chemical composition of neat and hydrogenated oil was established by high-resolution gas chromatography (HRGC) with flame ionization (FID) and mass spectrometric (MS) detection. The principal components of orange oil were monoterpenes (limonene 94.00%, α-pinene 0.54%, sabinene 0.74%, ß-myrcene 1.18%), followed by oxygenated compounds such as alcohols (linalool 0.89% and α-terpineol 0.06%) and aldehydes (citral- Z 0.09%, citral- E 0.14%, citronellal 0.07%). HRGC-FID-MS analysis of the hydrogenated mixtures revealed the presence of over twenty components, mainly the products of hydrogenation of limonene, citral, linalool, ß-myrcene, sabinene and ß-ocimene. α-Pinene and aliphatic aldehydes did not react under these conditions. The appearance of α-terpinolene and the increase of γ-terpinene concentration from 0.05% to 0.15% in the modified oils indicated isomerization associated with hydrogenation. Citral ( E- and Z-) was converted into citronellal (0.06–0.12%) and dihydrocitronellal (0.06–0.16%). Linalool was transformed into 3,7-dimethyl-1-octen-3-ol (0.42–0.63%) and 3,7-dimethyloctan-3-ol (0.11–0.32%). Various isomers formed by H 2 addition to the endo and exo double bonds in limonene constituted the main products (up to 95%) in the hydrogenated orange oils. The concentration of hydrogenated products increased from 62.78 to 89.76% when the temperature dropped from 80 to 60°C at a catalyst concentration of 0.5% (w/w). A smaller change was observed with 0.75% (w/w) catalyst.

A Total Synthesis of Taxol

The intramolecular Heck reaction of 1 to 2 is the cornerstone of this total synthesis of taxol (see conversion below). The route starts with the (S)-Wieland Miescher ketone, and the oxetane ring is installed early in the synthesis. Elaboration to a CD ring fragment, addition of an A ring nucleophile, and further manipulations yield the appropriate starting material (1) for the Heck reaction. After this key step yielding 2, the synthesis of baccatin III (and thence taxol) concludes with the cleavage of the exo double bond at C-10 and oxygenation at C-9 and C-13.

ChemInform Abstract: Synthesis of Medium Ring 1,5-Dienes.

Medium ring compounds (9 to 11 membered rings) having endo (E or Z) and exo double bonds at 1,5-positions were synthesized by intramolecular cyclization of the ω-functionalyzed allylic anion stabilized by a sulfur atom. The yields of cyclization were related not only with the cyclization enthalpy (steric strain of the resultant cyclic compounds) but also with entropy factor.

Synthesis of Medium Ring 1,5-Dienes

Abstract Medium ring compounds (9 to 11 membered rings) having endo (E or Z) and exo double bonds at 1,5-positions were synthesized by intramolecular cyclization of the ω-functionalyzed allylic anion stabilized by a sulfur atom. The yields of cyclization were related not only with the cyclization enthalpy (steric strain of the resultant cyclic compounds) but also with entropy factor.

Preparation of 5-alkyl-3-carboxymethylrhodanines and their aldose reductase inhibitory activity.

5-Alkyl-3-carboxymethylrhodanines (2) were prepared from 5-alkylmethylidene-3-carboxymethylrhodanines (1). The exo double bond of 1 was successfully reduced with NaBH4. The 1,4-addition reaction path was confirmed on the basis of proton nuclear magnetic resonance spectrum of the product (4b) obtained from the reduction of 3 using NaBD4. Optical resolution of the tert-butyl compound (2i) was achieved upon epimerization-crystallization method using L-3-amino-epsilon-caprolactam. The alkyl compounds (2) and the optical active compounds ((+)-2i, (-)-2i) were evaluated for aldose reductase inhibitory potency.

New facile synthesis of substituted 2-benzylidene-pyrrolidines by the anionic cyclization of δ-alkynylamines

Treatment of δ-alkynylamines with butyllithium or lithium aluminum hydride brought about a facile anionic cyclization, giving high yields of the corresponding enamine pyrrolidines having an exo double bond.

ChemInform Abstract: Geometric Structure and Energetics of Small Strained Hydrocarbons Involving an Exo Double Bond. A Combined Semiempirical and ab initio Study.

ChemInformVolume 18, Issue 38 Physical Organic Chemistry ChemInform Abstract: Geometric Structure and Energetics of Small Strained Hydrocarbons Involving an Exo Double Bond. A Combined Semiempirical and ab initio Study. M. ECKERT-MAKSIC, M. ECKERT-MAKSIC Dep. Org. Chem. Biochem., Inst. "Ruder Boskovic", 41001 Zagreb, Yugosl.Search for more papers by this authorZ. B. MAKSIC, Z. B. MAKSIC Dep. Org. Chem. Biochem., Inst. "Ruder Boskovic", 41001 Zagreb, Yugosl.Search for more papers by this authorA. SKANCKE, A. SKANCKE Dep. Org. Chem. Biochem., Inst. "Ruder Boskovic", 41001 Zagreb, Yugosl.Search for more papers by this authorP. N. SKANCKE, P. N. SKANCKE Dep. Org. Chem. Biochem., Inst. "Ruder Boskovic", 41001 Zagreb, Yugosl.Search for more papers by this author M. ECKERT-MAKSIC, M. ECKERT-MAKSIC Dep. Org. Chem. Biochem., Inst. "Ruder Boskovic", 41001 Zagreb, Yugosl.Search for more papers by this authorZ. B. MAKSIC, Z. B. MAKSIC Dep. Org. Chem. Biochem., Inst. "Ruder Boskovic", 41001 Zagreb, Yugosl.Search for more papers by this authorA. SKANCKE, A. SKANCKE Dep. Org. Chem. Biochem., Inst. "Ruder Boskovic", 41001 Zagreb, Yugosl.Search for more papers by this authorP. N. SKANCKE, P. N. SKANCKE Dep. Org. Chem. Biochem., Inst. "Ruder Boskovic", 41001 Zagreb, Yugosl.Search for more papers by this author First published: September 22, 1987 https://doi.org/10.1002/chin.198738053Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume18, Issue38September 22, 1987 RelatedInformation

Geometric structure and energetics of small strained hydrocarbons involving an exo double bond: a combined semiempirical and ab initio study

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTGeometric structure and energetics of small strained hydrocarbons involving an exo double bond: a combined semiempirical and ab initio studyM. Eckert-Maksic, Z. B. Maksic, A. Skancke, and P. N. SkanckeCite this: J. Phys. Chem. 1987, 91, 11, 2786–2790Publication Date (Print):May 1, 1987Publication History Published online1 May 2002Published inissue 1 May 1987https://doi.org/10.1021/j100295a028RIGHTS & PERMISSIONSArticle Views51Altmetric-Citations18LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (688 KB) Get e-Alerts

Vibrational force fields for strained hydrocarbons involving exo-double bonds. An ab initio study

Ab initio calculations of stretching force constants for the carbon-carbon double bond in a series of molecules characterized by different amounts of strain in the neighbourhood of the double bond were performed. The stretching force constants for bonds adjacent to the double bond have also been calculated as well as all relevant coupling terms. The variation in the force constant for the double bond is in agreement with the variations in bond distance predicted previously. Furthermore, it appears that the stretching force constants are linearly related to the product of s-character of the hybrids forming the bond in question, if other effects remain roughly constant. This seems to be the case in a series of studied molecules. It turns out that the strength of an exo-double bond is proportional to the amount of the angular strain inherent in the ring fragments attached to the double bond.

The chromatographic behaviour of cycloolefins on stationary phases of different polarity. Prediction of their retention indices and boiling points

The retention indices of mono and polycycloolefins with endo or exo double bonds, on squalane or polypropylenglycol 425 are related to their physico-chemical properties such as boiling point, molar volume, molar refraction, and refractive index. Equations have been empirically obtained, from which accurate retention indices of these compounds can be predicted. Unknown boiling points of some of these compounds can also be calculated from their lineal relation with the retention index on squalane.

キノノイド構造を有する拡張環状交差共役系の化学

One of the recent advances in the field of non-benzenoid aromatics would be the chemistry of the extended cyclic cross-conjugated compounds derived by insertion of more complex conjugated π-electron system instead of the exo-double bond in fulvene-, fulvalene-, annulenone-, and oxocarbon-systems. Many physical and chemical properties of remarkable interest have been developed in these newly designed cross-conjugated variations. The present review deals with the chemistry of quinarenes, quinarenones, quinocarbons, and their hetero analogs which are the extended cyclic cross-conjugated π-electron systems comprising one or more quinonoid structures. The fundamental insights mentioned here would provide helpful suggestions for the molecular design of organic dyes, highly polarized compounds, electron acceptors or electron donors having a bright prospect of developing the new field of application to the optoelectronics, organic super conductors, and so on.

Serrulatolosid, ein neues Iridoid-glucosid ausPenstemon serrulatus1

From leaves of PENSTEMON SERRULATUS Menz. a new iridoid glucoside of unusual type in having an exo double bond at C-8 on the cyclopentane-ring has been isolated. The structure of serrulatoloside has been established by spectroscopic methods.

Synthesis of (±)Dehydroxyglaupalol and Analogs

Abstract The natural furocoumarin dehydroxyglaupalol and two analogs were prepared by reaction of the appropriate 4-hydroxy-coumarin with 3-chloro-3-methylbutyne in basic medium, followed by catalytic hydrogenation of the exo double bond.

Synthesis of mono and difunctional oligoisobutylenes—IV. Modification of α,ω-dichlorooligoisobutylene by reaction with maleic anhydride. Preliminary study on block polycondensation

Thermal dehydrochlorination of α,ω-dichlorooligoisobutylene leads to the formation of both endo and exo double bonds; endo bonds are mainly those of 4-phenyl-2,4-dimethyl-2-pentene; exo double bonds belong either to “short” end-groups. Reaction of dichlorinated oligomers with maleic anhydride gives a mixture of oligomers with anhydride or substituted propenyl or indanic terminations. Pure α,ω-di(2-methyl-2-propenyl)oligoisobutylene was prepared by basic dehydrochlorination of α,ω-dichlorinated oligomer; only exo double bonds are formed. This α,ω-unsaturated oligomer reacts with maleic anhydride, giving an oligomeric mixture with functionality, with respect to anhydride, of 1.25 but containing endo double bonds and indane rings. When a catalyst is added (dichloromaleic anhydride), two molecules of anhydride can react with the same end of chain. Various polyamides were prepared from the α,ω-dianhydride oligomers.

The thermal rearrangements of methylenecyclopropanecarboxylic acids

Substituted methylenecyclopropanecarboxylic acids (6) and (7) rearrange thermally in the liquid phase to mixtures of the lactone (10) and the dihydrofuranone (13). The product ratios depend on the positions of the substituents. The parent acid (5) and Feist's acid (1a) decompose thermally in the presence of water to give ethyl methyl ketone and levulinic acid respectively. The mechanistic rationale of the above reactions is based on a competition between ring cleavage and electrophilic addition to the exo-double bond.