A highly enantioselective three-component coupling of 1,3-butadiene with a variety of fluorinated or nonfluorinated alkyl halides and aldehydes has been achieved relying on a Cr/Co bimetallic ...catalysis system. The strategy established here facilitates straightforward introduction of the privileged fluoro functionalities into homoallylic alcohols from bulk feedstock materials in a highly anti-diastereo and enantioselective manner.
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•Metal-catalyzed asymmetric difunctionalization of conjugated dienes in a highly regioselective fashion are realized.•Eight metal catalysts are introduced by the number of ...frequency.•Exquisite choosing diene coupling partners and reaction conditions are crucial for the high efficiency.
1,3-Dienes and derivatives are either feedstock chemicals or easily available materials. Catalytic difunctionalization of 1,3-diene is one of the most powerful methods for carboncarbon bond formation with rapid increase of the molecular complexity and synthetic value in an atom economic way. By choosing proper metals and chiral ligands, a variety of catalytic asymmetric difunctionalization of conjugated dienes in a highly regioselective fashion have been reported. In this digest review, we will summarize recent advances on this topic based on different metals. We will also introduce unique phenomena that include reversal of regio- and diastereoselectivity.
A visible-light-induced copper-catalyzed intermolecular hydroamination of alkenes using commercially accessible primary and secondary amines has been established. This effective method exhibits good ...tolerance of a broad range of functional groups and provides a facile access to an array of valuable amines with Markovnikov regioselectivity. The process can be positively expected to be used in bioactive amines, and it may provide new potential in the discovery of copper-catalyzed hydrofunctionalization reactions.
A photoinduced, copper-catalyzed, highly enantioselective dual alkylation/arylation and alkynylation of alkene is reported. A single chiral copper(I) complex serves to enable photoredox catalysis ...and induce enantioselectivity during the reaction. This reaction couples three different components under mild reaction conditions, exhibits a broad substrate scope, and provides facile access to chiral propargylic systems, including those featuring valuable fluorinated substituents.
Asymmetric allylation of aldehydes with γ-disubstituted allyl halides has been achieved in the presence of a sulfonamide/oxazoline chromium complex. A variety of synthetically useful α-homoallylic ...alcohols with two consecutive stereogenic centers, including one quaternary carbon, can be accessed in a highly diastereoselective and enantioselective manner.
Oxidizing gold? A gold(I)/gold(III) catalytic cycle is essential for the first oxidative cross-coupling reaction in gold catalysis. By using Selectfluor for gold(I) oxidation, this chemistry reveals ...the synthetic potential of incorporating gold(I)/gold(III) catalytic cycles into contemporary gold chemistry and promises a new area of gold research by merging powerful gold catalysis and oxidative metal-catalyzed cross-coupling reactions.
Abstract
Cyclobutanols are privileged cyclic skeletons in natural products and synthetic building blocks. C(sp3)−H functionalization is a prolonged challenge in organic synthesis. The synthesis of ...cyclobutanols through double C(sp3)-H bond functionalization remains elusive. Here we report the efficient synthesis of cyclobutanols through intermolecular radical 3 + 1 cascade cyclization, involving the functionalization of two C − H bonds through sequential hydrogen atom transfer. The copper complex reduces the iodomethylsilyl alcohols efficiently under blue-light irradiation to initiate the tandem transformation. The mild reaction tolerates a broad range of functional groups and allows for the facile generation of elaborate polycyclic structures.
DC-link electrolytic capacitor critically affects the lifetime of the motor drive system. This paper proposes an inverter power control strategy based on dc-link voltage regulation for the ...electrolytic capacitor-less interior permanent magnet synchronous motor drive system. The dc-link electrolytic capacitor is replaced by a small film capacitor and the power factor correction circuit is also eliminated. Hence, the inverter power should be regulated effectively to achieve high input power factor and low grid current harmonics. The inverter power control loop based on proportional resonant (PR) controller is established to regulate the inverter power into sinusoidal wave. The PR controller can be designed to achieve a high gain at the desired frequency and the parameters are easy to design due to the simple structure. In addition, a power compensation method based on the dc-link voltage regulation is used to diminish the error of inverter power control, which does not depend on the precise calculation and is easy to realize. The effectiveness of the proposed method is demonstrated by the experimental results on an air conditioner. The input power factor can reach 0.992 and the harmonics of grid current are considerably lower than the requirement of EN61000-3-2 standard.
Investigation on the long-term thermal response of precast high-strength concrete (PHC) energy pile is relatively rare. This paper combines field experiments and numerical simulations to investigate ...the long-term thermal properties of a PHC energy pile in a layered foundation. The major findings obtained from the experimental and numerical studies are as follows: First, the thermophysical ground properties gradually produce an influence on the long-term temperature variation. For the soil layers with relatively higher thermal conductivity, the ground temperature near to the energy pile presents a slowly increasing trend, and the ground temperature response at a longer distance from the center of the PHC pile appears to be delayed. Second, the short- and long-term thermal performance of the PHC energy pile can be enhanced by increasing the thermal conductivity of backfill soil. When the thermal conductivities of backfill soil in the PHC pile increase from 1 to 4 W/(m K), the heat exchange amounts of energy pile can be enhanced by approximately 30%, 79%, 105%, and 122% at 1 day and 20%, 47%, 59%, and 66% at 90 days compared with the backfill water used in the site. However, the influence of specific heat capacity of the backfill soil in the PHC pile on the short-term or long-term thermal response can be ignored. Furthermore, the variation of the initial ground temperature is also an important factor to affect the short-and-long-term heat transfer capacity and ground temperature variation. Finally, the thermal conductivity of the ground has a significant effect on the long-term thermal response compared with the short-term condition, and the heat exchange rates rise by about 5% and 9% at 1 day and 21% and 37% at 90 days as the thermal conductivities of the ground increase by 0.5 and 1 W/(m K), respectively.
Gold rush: A combination of oxidative gold(I)/gold(III) catalysis and CH functionalization led to the first oxidative coupling between in situ generated alkyl gold reagents and C sp 2H bonds, ...affording tricyclic indolines through a formal 3+2 annulation between a vinyl group and an aniline moiety see scheme; Tf=trifluoromethanesulfonyl, Selectfluor=1‐chloromethyl‐4‐fluoro‐1,4‐diazoniabicyclo2.2.2octane bis(tetrafluoroborate).
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