Substituent Effect on the Electronic Structure of Sulfines: Molecular Orbital Treatment

The electronic structure and ground state properties of the gaseous sulfine H₂CSO and some of its derivatives were studied at the RHF, MP2, and B3LYP levels. The calculations showed that the Z-isomer is more stable than the E-one and their difference in energy depends on their level of calculation, basis set, and substituent. The factors affecting the isomer stability are the electrostatic interactions, the steric factor, and π-electrons delocalization. The substituent has little effect on the geometry of the CSO moiety but greatly affects its charge distribution and polarizability. The ΔE value of the E- to Z-isomerization process via rotation of the S═O bond was calculated. The substituent has an appreciable effect on both the geometry and energy barrier of isomerization depending on its electronegativity, electrostatic attraction, and effect on π-delocalization over the molecule.     

Synthesis and Isolation of α-Oxo Sulfines

The synthesis of several α-oxo sulfines is discribed. Various α-oxo sulfines can be isolated as such. The Diels-Alder reaction of these sulfines with 1,3-dienes can be catalyzed by Lewis acids.     

New Structures from Multiple Rearrangements of Propargylic Dialkoxy Disulfides

Abstract

Sundry dipropargyloxy disulfides have been successfully prepared and their rearrangement paths and products have been found to be dependent upon their substitution pattern. Inter alia compounds of two heretofore unknown structure types— 10 and 11 on the one hand and 14 and 15 on the other—have been obtained and characterized.     

Push-pull amino succinimidyl ester thiophene-based fluorescent dyes: synthesis and optical characterization

The design and synthesis of new fluorescent dyes with emission range at 490-650 nm are described. Their structural and electronic properties have been characterized by both experimental techniques and quantum-chemical calculations. The chromophores are donor-π-bridge-acceptor push-pull compounds with a π bridge of phenyl and thiophene rings and their combination. Compared with previous thiophene fluorophores, these dyes show significant redshift in the absorption and emission spectra and offer compact, red-emitting fluorophores. The dyes have amino succinimidyl active ester and can be readily conjugated to proteins, polymers and other amino-group-containing materials.     

烯亚砜化合物的制备及反应概述

烯亚砜作为一类重要的反应中间体在有机合成领域发挥着重要应用。常见的烯亚砜制备方法包括:硫羰基化合物氧化、亚磺酰衍生物β-消除反应、改进的Peterson反应、重氮甲基亚砜的杂原子-Wolff重排反应等。作为活性中间体的烯亚砜可以被亲核试剂进攻硫原子中心或者碳原子中心,分别得到亚砜化合物或者新的烯亚砜物种;而其自身亦可以作为亲核试剂,以氧原子作为亲核位点与其他亲电试剂反应。烯亚砜和酰基或者烯基烯亚砜可以分别作为亲双烯体或双烯体发生正常和逆电子需求的Diels-Alder反应。烯亚砜既可以作为亲偶极子,也可以作为偶极子发生偶极环加成反应。此外,烯亚砜自身还可以发生二聚、脱硫等反应。希望本文总结的内容能够对该研究领域感兴趣的化学工作者有所帮助,并促进烯亚砜化学的进一步发展。     

Tandem sigmatropic rearrangements and cyclizations of propargylic dialkoxy disulfides

The first successful preparation of propargylic dialkoxy disulfides in high yields is reported. These esters afforded novel 6,7-dithiabicyclo[3.1.1]heptane-2-one 6-oxide derivatives via an unprecedented sequence of three [2,3]- and one [3,3]-sigmatropic shifts followed by an intramolecular [2+2] cycloaddition. The latter are structurally related to the zwiebelanes, recently isolated from freshly cut onion.     

Novel generation and ring closure of 1,3-thiaza-1,3-butadiene S-oxides through thermal cycloreversion of 6H-1,3,5-oxathiazine S-oxides

Heating of 6H-1,3,5-oxathiazine S-oxides efficiently afforded 1,2,4-oxathiazoles through the mechanism involving thermal cycloreversion of the substrates and the subsequent ring closure of the intermediary 1,3-thiaza-1,3-butadiene S-oxides.