A highly enantioselective Michael addition of allomaltol (5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one) to both aromatic and aliphatic β,γ‐unsaturated α‐ketoesters has been realized. Under the catalysis of a chiral bifunctional tertiary amine‐squaramide that bears a (1R,2R)‐1,2‐diphenylethane‐1,2‐diamine scaffold, the reaction proceeded smoothly with high levels of enantioselectivity to give the desired products in acceptable yields with 86–>99 % enantiomeric excess. This methodology provided an efficient process for the enantioselective synthesis of optically active kojic acid derivatives.
A bifunctional squaramide based on (R,R)‐11,12‐diamino‐9,10‐ethylene‐9,10‐dihydroanthracene has been developed, and it has demonstrated great advantages over previously reported organocatalysts in the asymmetric Michael addition of 4‐hydroxycoumarins to β,γ‐unsaturated α‐oxophosphonates. Upon quenching the generated β‐4‐hydroxy‐2‐oxo‐2H‐chromen‐3‐yl‐substituted acylphosphonate intermediates with DBU and an alcohol or amine as a second nucleophile, the corresponding β‐substituted carboxylates or amides were obtained in acceptable to excellent yields and with high levels of enantioselectivity (80–97 % ee) in a one‐pot fashion.
Abstract. According to the principle of "eagle eye", assuming that in the absence of the wind and air density uniform, tennis because of deformation produced by hitting, accurate to tennis in flight by gravity, air resistance, the tennis movement into the vertical direction and horizontal direction. Solution can be obtained using the ideas of calculus, thus draws the tennis range, fall to the ground, placement time and location. Increase the rotation of the tennis, according to the formula of sports biomechanics, the pressure difference to produce in vertical direction of the velocity and angular velocity magnus force, solving the stead yunus force coefficient, through the best tennis in the vertical direction of the time needed for higher level computation, model are described in detail in tennis trajectories of the rotating cases and placement, and intuitive simulation diagram of the flying track.
A highly diastereo- and enantioselective cyclopropanation of β,γ-unsaturated α-ketoesters with bromonitromethane has been successfully developed through a domino Michael-addition/intramolecular-alkylation strategy. Acceptable yields (up to 89%) and enantioselectivities (up to 96% ee) have been obtained.
Abstract. This article USES the automatic identification of human body joint point in the process of sports science algorithm, as a key point to discuss, in order to more realistic three-dimensional reconstruction basis of science. Through the body's automatic identification of the key software implementation process research, and in this paper, the image processing model to reconstruct the human body model according to the proportion principle in the late. Using camera measurement instruments and scientific measurement method, provides effective scientific data collection. Research results, to determine the link of 15 and 21 key points of the body, and gives the mathematical model of each joint point determined to establish the discriminate model of special circumstances, are visible side joint point enter human body contour line, invisible side joint point of shade and hands on hip to determine the influence of processing method.
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