The aldehydes installation by radical formylation constitutes an attractive synthetic strategy. However, the generation of formyl radicals for organic synthesis applications remains unknown. Herein we report the first formyl radical generation from α‐chloro N‐methoxyphthalimides, which selectively synthesize aldehydes by alkene hydroformylation under mild photoredox conditions. The aldehydes can be installed on acrylates, acrylamides, vinyl sulfones, vinyl ketones, and complex steroids by radical hydroformylation in excellent chemoselectivity and regioselectivity. The concerted hydrochloride elimination for the formyl radical generation from α‐chloro methoxy radicals is established by experimental and computational approaches.
Transition-metal-catalyzed transformation reactions of
epoxides
can provide practical C2 synthons in synthetic chemistry. These reactions
offer a feasible strategy for catalyst-controlled epoxide divergent
transformations. Therefore, finding out the crucial factors controlling
chemoselectivity is the key to the rational design of transition-metal-catalyzed
divergent conversions with high selectivity. In these studies, we
have selected and systematically explored the general mechanism of
both Mn(CO)5
–- and Co(CO)4
–-catalyzed divergent epoxide transformations associated
with different products, namely, alkenes and β-lactones. Our
computational studies showed that the chemoselective reaction undergoes
either a retro-[3 + 2] step forming an alkene or a carbonyl migration
insertion step for generating a β-lactone. For the Mn-catalyzed
reaction, the energy barrier of the retro-[3 + 2] step is lower than
that of the carbonyl migration insertion step, but the case is reversed
in the Co-catalyzed reaction. Further analysis revealed that the spatial
configurations of metal complexes and Pauli repulsion controlled by
the metal atomic radius could be responsible for the phenomenon. The
insights obtained are not only important for understanding chemoselectivity
determined by the inherent properties of transition metals but also
provide a valuable case for studying transition-metal-catalyzed reactions
with catalyst-controlled chemoselectivity.
Source apportionment of surface water is essential for effective pollution control and sustainable water management. Physical mechanism models usually need so much data and parameters for calibration that their application for complex hydrologic condition watershed becomes difficult. However, reverse source tracing methods only based on water quality parameters present a certain subjectivity and uncertainty. In this research, additional land-use parameters were applied as an auxiliary in principal component analysis (PCA) for accurate identification of pollution sources. Thirteen water quality parameters and two meteorology parameters were used in the PCA and absolute principal component score–multiple linear regression (APCS–MLR) model to quantitatively identify potential pollution sources and their contributions to surface water pollution of the Poyang Lake Basin, in which frequent flow and sediment flux exchange with Yangtze River make the river–lake relationship complex. The results showed that urban wastewater with 34% contribution and agricultural non-point sources with 16% contribution, were the major sources of pollution in water quality. TP and NH3–N, the most serious pollutants, causing agricultural non-point source pollutions with 40% contributions and urban wastewater with 21% contributions were the major sources in the Poyang Lake Basin. Urban wastewater with 60% contributions was the major source of organic contamination. It can be concluded that with associated land-use parameters, the GIS approach with the APCS–MLR model can improve the accuracy and certainty of source apportionment, providing aid decision information for managers on protection of surface water quality.
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