Visible-Light-Promoted Deoxygenative Alkylation of Quinoxalin-2(1H)-ones with Activated Alcohols.

A one-pot strategy for deoxygenative alkylation of alcohols with quinoxalin-2(1H)-ones was developed by using xanthate salts as alcohol-activating groups for radical generation in the presence of tricyclohexylphosphine under visible-light-promoted conditions. The remarkable features of this reaction include a broad substrate scope, excellent functional group tolerance, mild conditions, and simple operation. Moreover, the synthetic utility of this reaction was validated by the success of two-step one-pot reactions, scale-up synthesis, and chemoselective radical monodeoxygenation of diols.

[Effects of heterogeneous habitats on the coexistence of aquatic ecotype Alternanthera philoxeroides and Paspalum paspaloides]. / 异质生境对水生型空心莲子草-åŒç©—é›€ç¨—å ±å­˜çš„å½±å“.

Species coexistence depends on the comprehensive effects of biological properties and habitat heterogeneity. Based on a large-scale field survey (21°-35° N), we compared the differences on morphological and stoichiometric characteristics between the invasive aquatic species Alternanthera philoxeroides and the native co-occurring species Paspalum paspaloides, and examined the effects of environmental factors on such differences. The results showed that the coverage and importance value (IV) of A. philoxeroides were all significantly greater than P. paspa-loides (34.3% and 104.0%, respectively), whereas the height of P. paspaloides was significantly greater than A. philoxeroides (13.8%). Moreover, the total nitrogen concentration (TN) and N:P of A. philoxeroides were significantly greater than those of P. paspaloides (55.1% and 55.8%, respectively), whereas the total carbon concentration (TC) and C:N of P. paspaloides were significantly greater than those of A. philoxeroides (4.1% and 83.8%, respectively). A. philoxeroides coverage increased with the increases of longitude, and its abundance increased with the increases of water nitrate concentration and longitude, while its IV increased with the increases of water ammonium concentration. However, the coverage, abundance, and IV of P. paspaloides decreased with the increases of ammonium concentration. C:N of A. philoxeroides decreased with the increase of ammonium concentration. Increased mean annual temperature and mean annual precipitation increased C:N but decreased N:P of P. paspa-loides. The C:P of both species decreased with the increases of ammonium concentration and electrical conductivity. N:P of A. philoxeroides was little affected by environment. These results indicated that A. philoxeroides had greater coverage and N absorption capacity than P. paspaloides, and that enriched water nitrogen would aggravate the invasion of A. philoxeroides. Meanwhile, P. paspaloides improved its C-assimilate reserves and chose the growth competition strategy for resisting A. philoxeroides invasion under the superior hydrothermal conditions. Different responses to environmental changes contributed to their coexistence in aquatic ecosystem.