A new method has been developed for the catalytic enantioselective 1,3-dipolar cycloaddition of the Seyferth-Gilbert reagent (SGR) to isatylidene malononitriles using a cinchona alkaloid derivative as a catalyst. This method allowed for the synthesis of a series of chiral spiro-phosphonylpyrazoline-oxindoles in good yields with excellent enantioselectivities. The synthetic utility of this method was further demonstrated by its use in a three-component domino reaction involving isatin, malononitrile, and SGR based on sequential Knoevenagel condensation and 1,3-dipolar cycloaddition reactions.
An array of chiral [1,2,4]triazino [5,4-a]isoquinoline derivatives were obtained in excellent yields (up to 98%) and with excellent enantioselectivities (up to 99% ee) via a new highly asymmetric (3 + 3) cycloaddition reaction of diazo compounds and isoquinolinium methylides, with a bifunctional chiral phasetransfer catalyst (PTC). Density functional theory calculations show that PTC has a bridge role in the deprotonation/protonation process. The obtained products were transformed into densely functionalized polycyclic heterocompounds with multiple stereocenters.
The purpose of this paper is to investigate the effect of manufacturing errors on the performance of a gas-dynamic bearing gyroscope. Five kinds of manufacturing errors including bearing taper error, oval error, trigone error, eccentricity of the axis, and angular deviation of the axis are studied. A mathematic model of these errors is established to describe the variation of gas film thickness. The Reynolds equation is solved, and the perturbation method is applied to analyze the performance of the gas-dynamic bearing with the manufacturing errors. Based on the analysis, the interference torque and overload limit are investigated to assess the effects of manufacturing errors. Results show that taper error will cause interference torque. Oval error or trigone error will cause interference torque with a radial specific force. The eccentricity or angular deviation of the axis will cause interference torque with any specific force. In general, the interference torque is small, which is 10–1000 times smaller than that under the condition of both radial and axial specific forces. The manufacturing errors also reduce the ultimate overload significantly. The taper error has the greatest influence on the gas-dynamic bearing gyroscope among the manufacturing errors studied in this paper.
An efficient enantioselective Mannich reaction of N-protected α-sulfones with β-benzenesulfonyl phosphonates was developed by using a chiral cinchona alkaloid-derived thiourea as a catalyst. This method was used to obtain a series of chiral α-sulfonyl-β-aminophosphonates in yields of up to 96% with 89:11 dr and 88% ee. These compounds were further transformed into β-aminophosphonates or chiral azetidines with various functional groups by a Horner–Wadsworth–Emmons/aza-Michael addition reaction sequence.
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