Refernces
10.1021/ja00309a059
The research focuses on the structural effects of spin-orbit coupling (SOC) as a mechanism of intersystem crossing (ISC) in triplet-derived biradicals. The study aims to demonstrate that SOC is significantly enhanced in biradicals with an acyl terminus compared to those with only hydrocarbon termini and that biradicals containing an acyl terminus prefer to undergo ISC in conformers with small end-to-end distances. The researchers measured the lifetimes of biradicals by monitoring their nanosecond transient UV absorption and found that the presence of an acyl terminus greatly increases the ISC rate constant, suggesting that SOC is the dominant mechanism in acyl-benzyl biradicals. The chemicals used in this process include acyl-benzyl biradicals, hydrocarbon termini, and various solvents such as methanol, acetonitrile, and cyclohexanol, among others, to study the solvent's effect on biradical lifetimes. The conclusions support the proposition that ISC in acyl-benzyl biradicals requires a nearly cyclic conformation with small end-to-end distances, and the magnetic field effect on ISC rate constants was observed, affirming the dominance of SOC in biradicals with an acyl terminus.
10.1016/S0040-4020(00)00626-8
The study presents an eco-friendly and cost-effective method for the tosylation of alcohols and selective monotosylation of diols using p-toluenesulfonic acid with metal-exchanged montmorillonite clay as a catalyst. The Fe3+-montmorillonite clay demonstrated the highest effectiveness among the tested catalysts, outperforming Zn2+, Cu2+, Al3+-exchanged montmorillonites and K10 montmorillonite. This method allows for the regioselective tosylation of diols to monotosylated derivatives with high purity, favoring the primary hydroxy group in the presence of secondary hydroxy groups. The catalyst's reusability over several cycles was consistent, as shown in the tosylation of cyclohexanol. This approach minimizes by-product formation, typically just water, and offers advantages such as ease of catalyst recovery, recyclability, and enhanced stability compared to traditional methods using sulfonyl chloride or anhydride with organic bases.
10.1039/P29960001367
The research focuses on the thermal decomposition of N-acyl-3,4-dihydro-1H-2,1-benzoxazines, which undergo a retro-Diels-Alder reaction to extrude formaldehyde and form N-acylazaxylylenes. These intermediates then undergo a 6a electrocyclisation to yield 2-substituted-4H-3,1-benzoxazines, rather than a 47c electrocyclisation which would lead to N-acyl-1,2-dihydrobenzazetes. The study provides a detailed characterization of the compounds formed using spectroscopic methods, revealing data inconsistent with previous reports, and suggests that the previously reported structures for these compounds may need to be reevaluated. The chemicals used in this process include a range of N-acyl-3,4-dihydro-1H-2,1-benzoxazines with different substituents (such as N-benzoyl, N-acetyl, N-pivaloyl, etc.), formaldehyde, and various solvents like mesitylene and cyclohexanol for the reactions.
Xn
Xn:Harmful;
