α-Substituent Effects on Si–H, P–H and S–H Bond Dissociation Energies

Abstract

CBS-Q and G3 methods were used to generate a large number of reliable Si-H, P-H and S-H bond dissociation energies (BDEs) for the first time. It was found that the Si-H BDE displayed dramatically different substituent effects compared with the C-H BDE. On the other hand, the P-H and S-H BDE exhibited patterns of substituent effects similar to those of the N-H and O-H BDE. Further analysis indicated that increasing the positive charge on Si of XSiH 3 would strengthen the Si-H bond whereas increasing the positive charge on P and S of XPH 2 and XSH would weaken the P-H and S-H bonds. Meanwhile, increasing the positive charge on Si of 2 XSiH i stabilized the silyl radical whereas increasing the positive charge on P and S in XPH • and XS • destabilized P-and S-centered radicals. These behaviors could be reasonalized by the fact that Si is less electronegative than H while P and S are not. Finally, it was demonstrated that the spin-delocalization effect was valid for the Si-, P-and S-centered radicals.

Formoxazine, a New Pyrrolooxazine, and Two Amines from the Marine–Mudflat‐Derived Fungus Paecilomyces formosus

“…Based on the biological activity of the pyrrolooxazines reported previously, compound 1 warrants further study for its potential chemotherapeutic value against cancer, CNS disorders, inflammatory diseases, and pathogenic infections.…”

“…Pyrrolooxazine derivatives, such as compound 1 , have been reported not only as the synthetic intermediates during the development of antagonists of C–X–C chemokine receptor type 7 (CXCR7) and metabotropic glutamate receptor subtype 5 (mGluR5), but also as synthetic anti‐inflammatory and analgesic compounds . CXCR7 antagonists are useful in preventing tumor cell proliferation, tumor formation, tumor vascularization, metastasis, and inflammatory disease, and the mGluR5 antagonist has wide potential therapeutic application in a variety of central nervous system (CNS) disorders.…”

Ethyl 2-{3-[(2-chloro-1,3-thiazol-5-yl)methyl]-4-nitroimino-1,3,5-triazinan-1-yl}acetate

“…We previously reported the synthesis and crystal structure of 3-methyl-1H-pyrrolo[2,1-c][1,4]oxazin-1-one (I) (Khan et al, 2010). The title compound (II), which was designed by changing the methyl substituent in (I) to phenyl, is a new key intermediate which can be used as a precursor for the syntheses of muscle relaxant agents (Bélanger et al, 1983) and other biological active compounds (Fu et al, 2002).…”

“…In the crystal, weak intermolecular C-HÁ Á ÁO interactions link molecules into chains along [110]. The crystal studied was an inversion twin with a 0.48624 (9):0.51376 (9) domain ratio.Related literatureFor the biological activity and applications of pyrrolo[1,2-a]pyrazine derivatives, see:Bé langer et al (1983);Fu et al (2002);Micheli et al (2008). For a related structure, see:Khan et al (2010).…”

Cross‐Linking Building Blocks Using a “Boronate Bridge” to Build Functional Hybrid Materials

“…In the 1990s–2000s, BAs were mainly used as molecular‐scale building blocks to construct discrete, “convergent” self‐assemblies formed by well‐designed molecular‐scale building blocks . However, in the most recent decade, BAs have begun to be used as parts of “divergent” self‐assemblies, leading to functional materials for sensors, separation tools, and biomedical applications …”