仿贝壳结构的自组装有机-无机纳米复合薄膜的制备及结构表征

利用超分子自组装法在玻璃表面制备了聚合前后DMTB/SiO2和DMCB/SiO2复合薄膜.在所制备的复合薄膜中,表面活性剂DMTB和DMCB既作结构导向剂,又作聚合单体.用FTIR,XRD和TEM等表征了薄膜的结构.结果表明,所制备的薄膜具有有机-无机有序交替的层状结构.DMCB/SiO2和DMTB/SiO2复合薄膜有机层与无机层间的距离分别为聚合前3.48和3.44nm,聚合后2.84和2.92nm.     

不同晶粒大小ZSM－5的合成和表征

采用水热合成法，由不同途径合成出晶粒大小不同的几种ＺＳＭ－５分子筛，这几种分子筛具有大致相同的硅铝比．采用ＮＨ３－ＴＧ－ＴＰＤ，Ｐｙｒｉｄｉｎｅ－ＩＲ－ＴＰＤ表征其酸性，用ＸＰＳ表征其外表面的硅铝比（体相的硅铝比用元素原子吸收法测定）．研究结果表明，应用导向剂可以合成出要求的晶粒大小而且粒度均匀；加晶种的合成得不到较大的晶体，粒度亦不均匀．分子筛的晶粒大小对其酸性有一定的影响，一般来讲，小晶粒分子筛的酸量多．本文中大晶粒分子筛的硅铝比基本上是不均匀的．     

Copper/Silver‐Mediated Direct ortho‐Ethynylation of Unactivated (Hetero)aryl CH Bonds with Terminal Alkyne

A copper/silver‐mediated oxidative ortho‐ethynylation of unactivated aryl C?H bonds with terminal alkyne has been developed. The reaction uses the removable PIP directing group and features broad substrate scope, high functional‐group tolerance, and compatibility with a wide range of heterocycles, providing an efficient synthesis of aryl alkynes. This procedure highlights the potential of copper catalysts to promote unique, synthetically enabling C?H functionalization reactions that lie outside of the current scope of precious metal catalysis.     

Lithiation of 2-(chloroaryl)-2-methyl-1,3-dioxolanes and application in synthesis of new ortho-functionalized acetophenone derivatives

2-(4-Chlorophenyl)-2-methyl-1,3-dioxolane 2a was lithiated ortho to the ketal group by treatment with butyllithium in THF at 0°C. Related 2-aryl-2-methyl-1,3-dioxolanes possessing a chlorine substituent at the meta position of the aryl group 2b,c were lithiated with butyllithium in THF at −78°C at the position between the two directing groups. The lithio species thus generated were treated with various electrophiles to give ortho-functionalized acetophenone derivatives.     

A Transient‐Directing‐Group Strategy Enables Enantioselective Reductive Heck Hydroarylation of Alkenes

Metal‐coordinating directing groups have seen extensive use in the field of transition‐metal‐catalyzed alkene functionalization; however, their waste‐generating installation and removal steps limit the efficiency and practicality of reactions that rely on their use. Inspired by developments in asymmetric organocatalysis, where reactions rely on reversible covalent interactions between an organic substrate and a chiral mediator, we have developed a transient‐directing‐group approach to reductive Heck hydroarylation of alkenyl benzaldehyde substrates that proceeds under mild conditions. Highly stereoselective migratory insertion is facilitated by in situ formation of an imine from catalytic amounts of a commercially available amino acid additive. Computational studies reveal an unusual mode of enantioinduction by the remote chiral center in the transient directing group.     

A Guide to Directing Group Removal: 8-Aminoquinoline

The use of directing groups allows high levels of selectivity to be achieved in transition metal-catalyzed transformations. Efficient removal of these auxiliaries after successful functionalization, however, can be very challenging. This review provides a critical overview of strategies used for removal of Daugulis’ 8-aminoquinoline (2005–2020), one of the most widely used N,N-bidentate directing groups. The limitations of these strategies are discussed and alternative approaches are suggested for challenging substrates. Our aim is to provide a comprehensive end-users’ guide for chemists in academia and industry who want to harness the synthetic power of directing groups—and be able to remove them from their final products.     

Silanol as a removable directing group for the Pd(II)-catalyzed direct olefination of arenes

Need some direction? Silanol was developed as a directing group for the Pd(II)-catalyzed oxidative Heck-type reaction of arenes. A one-pot C-H activation/desilylation process of benzyldiisopropylsilanol was also demonstrated, providing a powerful approach for the synthesis of ortho-alkenyl-substituted alkylarenes. Considering the easily attachable and readily removable properties of the silanol group, this reaction will find broad synthetic applications.