Lactone Radical Cyclizations and Cyclization Cascades Mediated by SmI₂–H₂O

Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI₂–H₂O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow “one-pot” access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl

Lactone Radical Cyclizations and Cyclization Cascades Mediated by SmI₂–H₂O

Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI₂–H₂O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow “one-pot” access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl

Lactone Radical Cyclizations and Cyclization Cascades Mediated by SmI₂–H₂O

Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI₂–H₂O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow “one-pot” access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl

Lactone Radical Cyclizations and Cyclization Cascades Mediated by SmI₂–H₂O

Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI₂–H₂O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow “one-pot” access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl

Lactone Radical Cyclizations and Cyclization Cascades Mediated by SmI₂–H₂O

Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI₂–H₂O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow “one-pot” access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl

Lactone Radical Cyclizations and Cyclization Cascades Mediated by SmI₂–H₂O

Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI₂–H₂O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow “one-pot” access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl

Can “Electric Flare Stacks” Reduce CO₂ Emissions? A Case Study with Nonthermal Plasma

Gas flare stacks are the current benchmark technology for industrial pollution control. However, their impact on human health and the environment is not negligible. If net zero CO2 emissions are to be achieved, their current significant CO2 impact (400 Mt y–1 globally, 2022) should be reduced. Herein, a model nonthermal plasma “electric flare stack” consuming 6.6% less energy than an equivalent steam aided methane flare, with significant CO2 emission reductions (between 2.0× and 11.4× lower), when removing isobutylene is demonstrated. Isobutylene streams in air (1.3% v/v) are completely and rapidly consumed (>99% at flow rates up to 125 mL min–1, 1 atm, RT) by the electrically generated nonthermal plasma in a linear flow reactor. At low powers (≤50 J L–1 specific input energy), the major degradation products (>95%) are a complex mixture of low-molecular-weight oxygenates, including acetone, isobutylene oxide, and isobutyraldehyde. Only small amounts of CO/CO2 (<5% selectivity) are generated (at 50 J L–1). Complete oxidation of isobutylene to CO2 (>99% selectivity) results when the plasma oxidation is coupled to a heterogeneous catalyst bed. For the optimal V2O5 catalyst, synergistic interactions between the plasma and V2O5 are evident, as positioning the catalyst after the plasma provides optimal reactor performance (two-stage vs single-stage oxidation). Placement of shorter catalyst beds close to the plasma discharge region gives optimal reactor performance

Reductive Cyclization Cascades of Lactones Using SmI₂−H₂O

Lactones bearing two alkenes or an alkene and an alkyne undergo reductive cyclization cascades upon treatment with SmI2−H2O, giving decorated azulene motifs in excellent yields with good diastereocontrol

Studies on the Mechanism, Selectivity, and Synthetic Utility of Lactone Reduction Using SmI₂ and H₂O

Although simple aliphatic esters and lactones have long been thought to lie outside the reducing range of SmI2, activation of the lanthanide reagent by H2O allows some of these substrates to be manipulated in an unprecedented fashion. For example, the SmI2−H2O reducing system shows complete selectivity for the reduction of 6-membered lactones over other classes of lactones and esters. The kinetics of reduction has been studied using stopped-flow spectrophotometry. Experimental and computational studies suggest that the origin of the selectivity lies in the initial electron-transfer to the lactone carbonyl. The radical intermediates formed during lactone reduction with SmI2−H2O can be exploited in cyclizations to give cyclic ketone (or ketal) products with high diastereoselectivity. The cyclizations constitute the first examples of ester-alkene radical cyclizations in which the ester carbonyl acts as an acyl radical equivalent

Studies on the Mechanism, Selectivity, and Synthetic Utility of Lactone Reduction Using SmI₂ and H₂O

Although simple aliphatic esters and lactones have long been thought to lie outside the reducing range of SmI2, activation of the lanthanide reagent by H2O allows some of these substrates to be manipulated in an unprecedented fashion. For example, the SmI2−H2O reducing system shows complete selectivity for the reduction of 6-membered lactones over other classes of lactones and esters. The kinetics of reduction has been studied using stopped-flow spectrophotometry. Experimental and computational studies suggest that the origin of the selectivity lies in the initial electron-transfer to the lactone carbonyl. The radical intermediates formed during lactone reduction with SmI2−H2O can be exploited in cyclizations to give cyclic ketone (or ketal) products with high diastereoselectivity. The cyclizations constitute the first examples of ester-alkene radical cyclizations in which the ester carbonyl acts as an acyl radical equivalent