Unusual Substituent Research Articles

ChemInform Abstract: Palladium(0)‐mediated Intramolecular Lactonization of Allylic Alcohol Derivatives; Unusual Substituent Effect of the Trifluoromethyl Group on δ‐Lactone Formation.

AbstractCyclization reaction of the allylic carbonates (I) and subsequent deethoxycarbonylation yield a mixture of the cis‐ or trans‐disubstituted δ‐lactones (II) and (III) with predominance of the former.

Highly enantioselective protonation of photodienols an unusual substituent effect on the induced chirality

Enantiosalectivities up to 91% have been reached during the photodeconjugation of α, β -unsaturated esters or lactones using catalytic amounts of new chiral cyclic inductors derived from (+) camphor. Modification of the substitution on the nitrogen of the inductor can reverse the configuration of the new chiral center.

Palladium(0)-mediated intramolecular lactonization of allylic alcohol derivatives; unusual substituent effect of the trifluoromethyl group on δ-lactone formation

In the Intramolecular lactonization of allylic alcohol derivatives catalysed by a palladium(0) complex, selective formation of 4,6-cis-disubstituted δ-lactones and the unusual effect of a trifluoromethyl group in the homoallylic position were observed.

ChemInform Abstract: An Unusual Substituent Effect on Elimination vs Fragmentation Reactions of the Dianions of 5‐Fluorouracil ‐ Alkene Photoadducts. Preparation of Cyclobutane‐Annelated Uracils.

AbstractAcetone sensitized cycloaddition reaction of 5‐fluorouracil (I) with the 2‐methoxy‐1‐alkenes (II) gives the photoadducts (III) and (IV).

An unusual substituent effect on elimination versus fragmentation reactions of the dianions of 5-fluorouracil-alkene photoadducts. Preparation of cyclobutane-annulated uracils

An unusual substituent effect on elimination versus fragmentation reactions of the dianions of 5-fluorouracil-alkene photoadducts. Preparation of cyclobutane-annulated uracils

ChemInform Abstract: Nucleophilic Addition to Olefins. Part 16. Unusual Substituent Effects in the Reaction of Amines with β‐Nitrostyrenes.

ChemInform Abstract: Nucleophilic Addition to Olefins. Part 16. Unusual Substituent Effects in the Reaction of Amines with β‐Nitrostyrenes.

Location and identity of the acyl substituents on the extracellular polysaccharides of Rhizobium trifolii and Rhizobium leguminosarum

The basic structures of the extracellular polysaccharides of Rhizobium leguminosarum and Rhizobium trifolii were found to be identical, but their acylation patterns differ. Liquid hydrogen fluoride at −40° degrades the two polysaccharides to a series of oligosaccharides representing the repeating units of the polysaccharides and their higher homologs. At −23°, it degrades the polymers to a mixture of oligosaccharides from which a tetrasaccharide constituting a unit of the backbone of the polysaccharide, and a trisaccharide representing all but the non-reducing terminus of the side chain, could be readily purified. The location and identity of the acyl substituents were determined by 1H-n.m.r. spectroscopy, methylation analysis, and f.a.b. mass spectrometry. The unusual substituent d-3-hydroxybutanoate was found esterified to O-3 of a terminal 4,6- O-pyruvic acetalated d-galactose in both strains of R. leguminosarum, and in one of the three strains of R. trifolii tested. All of the strains tested contained a 3- O-acetyl substituent on the (1→4)-β- d-glucopyranosyl residues in the backbone of the polysaccharide. Only the R. leguminosarum polysaccharides contained a combination of 2- and 3- O-acetyl groups on the branching sugar of the backbone of the polymer.

Unusual substituent effect on a palladium-mediated cyclization: a total synthesis of (.+-.)-sterepolide

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUnusual substituent effect on a palladium-mediated cyclization: a total synthesis of (.+-.)-sterepolideBarry M. Trost and John Y. L. ChungCite this: J. Am. Chem. Soc. 1985, 107, 15, 4586–4588Publication Date (Print):July 1, 1985Publication History Published online1 May 2002Published inissue 1 July 1985https://doi.org/10.1021/ja00301a056RIGHTS & PERMISSIONSArticle Views927Altmetric-Citations87LEARN 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 (369 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

β‐Thiocyanatovinylcarbonylverbindungen. XI. Ungewöhnliche Substituenteneffekte bei der massenspektrometrischen Fragmentierung von β‐Thiocyanatovinylaldehyden

β‐Thiocyanatovinylcarbonyl Compounds. XI. Unusual Substituent Effects in the Mass‐spectrometrical Fragmentation of β‐ThiocyanatovinylaldehydesThe mass spectra of homologous Z/E‐isomers and constitutional isomers of β‐thiocyanatovinylaldehydes are discussed. The main fragmentation consisting of HCN‐loss from the molecular ion is influenced by the substituents so that the constitutional and steric isomers can be clearly distinguished by the \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm M - HC}\left. {\overline {\, {\rm N} \,}}\! \right| + /{\rm M + }^ \cdot $\end{document} ratio. Alkyl homologues with a hydrogen atom in γ‐position to the aldehyde group show an unusual intensive CN‐radical loss due to a „hidden hydrogen rearrangement”︁, which was proved by deuteration experiments.

Experimental and theoretical investigation of the unusual substituent effect of the vinyl group

σ+ Substituent constants for the ortho- and para-vinyl group have been determined by the application of the linear free-energy relationship to the nitration of the β-substituted styrene derivatives.Energy changes (relative to benzene system) for the proton and hydride ion transfer to individual positions in the styrene molecule have been calculated. Both approaches indicate that the vinyl group is capable of stabilizing both positively and negatively charged transition states. The interactions of the vinyl group with other substituents in the phenyl ring are also determined. Again, stabilizing effects with respect to both π-donor and π-acceptor substituents have been demonstrated for the vinyl group.

Unusual substituent and multiplicity effects in carbenic ring expansion and substitution reactions of benzenes with 3-diazo-2,5-diphenylpyrrole

Unusual substituent and multiplicity effects in carbenic ring expansion and substitution reactions of benzenes with 3-diazo-2,5-diphenylpyrrole

Anthocyanins of the podocarpaceae

In the Podocarpaceae anthocyanins occur in some vegetative organs, and in seed-bearing structures where they have a comparable role to angiosperm fruit pigments. Pelargonidin and peonidin are recorded for the first time from gymosperms and several species contain pigments with an unusual substituent that confers highly characteristic chromatographic behaviour. Distribution of anthocyanins does not as yet aid substantially in the taxonomy of the principal genera.