Continuous-flow multi-step synthesis takes the advantages of microchannel flow chemistry and may transform the conventional multi-step organic synthesis by using integrated synthetic systems. To realize the goal, however, innovative chemical methods and techniques are urgently required to meet the significant remaining challenges. In the past few years, by using green reactions, telescoped chemical design, and/or novel in-line separation techniques, major and rapid advancement has been made in this direction. This minireview summarizes the most recent reports (2017–2020) on continuous-flow synthesis of functional molecules. Notably, several complex active pharmaceutical ingredients (APIs) have been prepared by the continuous-flow approach. Key technologies to the successes and remaining challenges are discussed. These results exemplified the feasibility of using modern continuous-flow chemistry for complex synthetic targets, and bode well for the future development of integrated, automated artificial synthetic systems. 相似文献
Levoglucosenone (LGO) is a cellulose-derived molecule that is present commercially on a multi-ton/year scale. Taking advantage of the α,β-conjugated ketone of LGO, a new citronellol-containing 5-membered lactone (HBO-citro) was synthesized through a one-pot two-step pathway involving oxa-Michael addition and Baeyer-Villiger oxidation. The solvent-free treatment of HBO-citro with NaBH4 at room temperature led to the full reduction of the lactone moiety which gave a novel fully renewable triol monomer having a citronellol side chain (Triol-citro). Noticeably, by simply changing the reducing agent, temperature and reaction duration, the partial reduction of HBO-citro can be achieved to yield a mixture of 5- and 6-membered Lactol-citro molecules. Triol-citro was chosen to prepare functional renewable polyesters having citronellol pendant chains via polycondensation reactions with diacyl chlorides having different chain lengths. Good thermal stability (Td5% up to 170 °C) and low glass transition temperatures (as low as −42 °C) were registered for the polyesters obtained. The polymers were then hydrolyzed using a commercial lipase from Thermomyces lanuginosus (Lipopan® 50 BG) to assess their biodegradability. A higher degradation profile was found for the polyesters prepared using co-monomers (acyl chlorides) having longer chain lengths. This is likely due to the decreased steric hindrance around the ester bonds which allowed enhanced accessibility of the enzyme. 相似文献
This paper investigates the quantum dense coding of a three-qubit XXZ Heisenberg spin chain at thermal equilibrium, with three-site interactions in the presence of an external magnetic field. We analyze the effects of various system parameters on the dense coding in multiple cases with different types of three-site interactions. The results show that the most ideal case for dense coding is the model including both types of three-site interactions, with the imposed condition of XZX + YZY type of three-site interaction is larger than the XZY − YZX type of three-site interaction. The inclusion of the z direction coupling parameter JZ, and external magnetic parameter B are found to be effective for optimizing the dense coding capacity, while the temperature T is turned out to be destructive. Moreover, the ferromagnet (FM) is shown to be more ideal for quantum dense coding than the antiferromagnet (AFM). For FM, by comparing the two types of three-site interactions (XZY − YZX and XZX + YZY), the appropriate model for valid dense coding is suggested and their dominant regions are clarified.
We investigate the joint effects of phase decoherence,Dzyaloshinskii-Moriya(DM) interaction and inhomogeneity of the external magnetic field(b) on dense coding in a two-qubit anisotropic Heisenberg XY Z spin chain.Analytical expressions are obtained for the dense coding capacity.It is found that valid dense coding is always possible with this model when the system is initially prepared in the maximum entangled state.Moreover,optimal dense coding can be implemented for this initial state as long as the mean spin-spin coupling constant J + of the XY plane is larger than b and the DM interaction despite the intrinsic decoherence.Non-maximal entangled initial states are found to be undesirable for dense coding with this model. 相似文献