This work reports gold‐catalyzed [3+2]‐annulations of α‐diazo ketones with highly substituted cyclopentadienes, affording bicyclic 2,3‐dihydrofurans with high regio‐ and stereoselectivity. The reactions highlights the first success of tetrasubstituted alkenes to undergo [3+2]‐annulations with α‐diazo carbonyls. The enantioselective annulations are also achieved with high enantioselectivity using chiral forms of gold and phosphoric acid. Our mechanistic analysis supports that cyclopentadienes serve as nucleophiles to attack gold carbenes at the more substituted alkenes, yielding gold enolates that complex with chiral phosphoric acid to enhance the enantioselectivity.
The cut-off valve based on pilot valve controlling is a new kind of valve which opens and closes fast and has low driving energy consumption. Because of the complexity of the internal flow and uncertainty of the internal pressure, there is uncertainty in the design of the key structure. We simulate the whole opening process of the valve under different key structural dimensions with Fluent Dynamic Mesh and UDFs, and we do experiments to authenticate simulation results. The turn-on time we get from the simulation is the same as that from experiments under the valves actual operating conditions, in other words, the simulation results are correct, so we can identify the valve flow and get the internal pressure data which provides a reliable basis for the design of the key structural dimensions.
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