Substituent

About: Substituent is a research topic. Over the lifetime, 42877 publications have been published within this topic receiving 516716 citations. The topic is also known as: side chain & side group.

A New Reaction Sequence Involving Palladium-Catalyzed Unsymmetrical Aryl Coupling

Abstract: Biphenylylalkenes containing an ortho substituent in one ring and a different ortho-, meta-, or para-substituent in the other are prepared in satisfactory yield from an ortho-substituted aryl iodide, an ortho-, meta-, or para-substituted aryl bromide, a terminal olefin, and a base in DMF under the joint catalytic action of palladium(0) and norbornene.

Model reaction for the synthesis of polyhydroxyurethanes from cyclic carbonates with amines: Substituent effect on the reactivity and selectivity of ring‐opening direction in the reaction of five‐membered cyclic carbonates with amine

Abstract: This article focuses on the substituent effect on the reactivity and selectivity of the ring-opening direction in the reaction of five-membered cyclic carbonates with n-hexylamine. The reactivity of the cyclic carbonate and the formation selectivity of the adduct with a secondary hydroxyl group increased as a stronger electron-withdrawing group was introduced at the α-methylene of the cyclic carbonate. These results are discussed on the basis of the stability of intermediates, primary and secondary alcoholate anions, Mulliken charges on carbonyl carbon, and the bond lengths and orders of the OCO single bond. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3678–3685, 2001

Synthesis and photophysical properties of borondipyrromethene dyes bearing aryl substituents at the boron center.

Abstract: Several borondipyrromethene (Bodipy) dyes bearing an aryl nucleus linked directly to the boron center have been prepared under mild conditions. The choice of Grignard or lithio organo-metallic reagents allows the isolation of B(F)(aryl) or B(aryl)2 derivatives; where aryl refers to phenyl, anisyl, naphthyl, or pyrenyl fragments. A single crystal, X-ray structure determination for the bis-anisyl compound shows that the sp3 hybridized boron center remains pseudo-tetrahedral and that the B−C bond distances are 1.615 and 1.636 A. All compounds are electrode active but replacement of the fluorine atoms by aryl fragments renders the Bodipy unit more easily oxidized by 100 mV in the B(F)(aryl) and 180 mV in the B(aryl)2 compounds whereas reduction is made more difficult by a comparable amount. Strong fluorescence is observed from the Bodipy fluorophore present in each of the new dyes, with the radiative rate constant being independent of the nature of the aryl substituent. The fluorescence quantum yields are sol...

Nuclear magnetic resonance spectroscopy. Carbon-13 chemical shifts of methycyclopentanes, cyclopentanols, and cyclopentyl acetates

Abstract: The ^(13)C chemical shifts of the title compounds have been determined by high-resolution nmr spectroscopy with the aid of proton decoupling. Substituent effects have been computed and compared to those obtained for some corresponding cyclohexane compounds, with the hope of providing information about steric interactions and conformations of cyclopentane derivatives. Rather large downfield ɑ (up to ~24 ppm) and β (up to ~7 ppm) shifts were observed on dissolution of up to 0.5 M europium tris(dipiva1omethane) in cyclopentanols. The cis- and trans-3-methyl- and 1,3-dimethylcyclopentanols showed somewhat different chelate shifts which could be used to help assign the stereochemical configuration of these substances. The ^(13)C chemical-shift changes produced by chain branching in some aliphatic acetates and ethers are compared and rationalized.