Visible-Light-Induced Cross-Dehydrogenative Coupling of Heteroarenes with Aliphatic Alcohols Mediated by Iodobenzene Dichloride

With the irradiation of visible light, α-heteroarylation of aliphatic alcohol was selectively achieved under gentle conditions in the present of iodobenzene dichloride. The Minisci-type cross-dehydrogenative coupling reaction was performed in the absence of metal and acid. Readily available primary alcohols and electron-withdrawing heteroarenes can be applied smoothly. Mechanism studies indicated that the PhICl radical and chlorine radical formed from iodobenzene dichloride were responsible for the selective hydrogen atom abstraction of alcohols.     

Metal-Free,Light-Mediated,Site-Specific,Radical C6−H Alkylation of Purines with Alcohols Intervened by Oxalates without Catalysts

Herein, we report the development of a radical deoxy-functionalization strategy for the direct C−H alkylation of purines and purine nucleosides with alcohols (1°, 2°, 3°) intervened by oxalates under 12 W blue LED irradiation. The reaction shows high regioselectivity at C6−H position of purine and is suitable for N9-, N7-substitued purines. The process accommodates purines and alcohols to deliver a wide range of products (31 examples) in 41–91 % yields, which avoids transition metal catalysts and organometallic reagents, and is not sensitive to moisture and air. Besides, the mild protocol displays broad functional groups tolerance and is easily up scalable to gram scale and can be used for late-stage C−H alkylation of purine to synthesize pharmaceutical 6-cyclopentyl nebularine with anti-CEM activity or natural d -menthol modification.     

Diamine‐Catalyzed Addition of ZnEt2 to PhC(O)CF3: Two Mechanisms and Autocatalytic Asymmetric Enhancement

NMR spectroscopic studies of the catalytic addition reaction of ZnEt₂ to PhC(O)CF₃ in the presence of three very efficient catalysts [TMEDA, tBuBOX, and L ; where L is a chiral diamine synthesized from optically pure (R,R)‐1,2‐diphenylethylenediamine and (S)‐2,2′‐bis‐(bromomethyl)‐1,1′‐binaphthalene] reveal large differences in their behavior. For the ligands TMEDA and tBuBOX, the catalysis shows no unusual features and proceeds via [(N?N)Zn(Et){OC(CF₃)(Et)Ph}]. For N?N? L , the observation of autocatalytic asymmetric enhancement during the catalysis, and unusual inverse concentration dependence on the reaction rate, indicate the participation of an additional novel catalytic cycle that goes through a dinuclear intermediate containing one ZnEt₂ and one ZnEt fragment connected by N?N and OR bridges. Interestingly, the ¹⁹F NMR signals of the main product of the reaction ([Zn(Et){OC*(CF₃)(Et)Ph}]₂) allowed us to assess the enantioselectivity of the processes in situ without the assistance of chiral chromatography.     

Highly regioselective Friedel-Crafts alkylation of indoles with α,β-unsaturated N-acylbenzotriazoles

The Friedel-Crafts alkylation rather than acylation of indoles was realized with α,β-unsaturated acylbenzotriazoles catalyzed by samarium(III) iodide under reflux in anhydrous THF. The reaction was highly regioselective, and a series of new 3-substituted indole derivatives were obtained in moderate to good yields with the potential to be further transformed into various indole derivatives due to the presence of active acylbenzotriazole moiety.     

Palladium(0)-catalyzed amination of allylic natural terpenic functionalized olefins

The palladium(0) catalyzed amination of allylic acetates and carbonates derivatives from terpenic olefins was carried out under mild conditions. The reaction offers a very good method for the preparation of allylic amines and thus to provide a useful entry to new functionalized terpenic olefin products. The mechanism involving a formation of p-allyl-palladium intermediate complex is in good agreement with the results obtained with the optically active substrates, as well as via an analysis of the observed regio-and stereoselectivity.      

Isotope effects and the mechanism of palladium-catalyzed allylic alkylation

The palladium-catalyzed allylic alkylation reaction of 1,1-dimethylallyl acetate with dimethyl malonate is studied by a combination of isotope effects and theoretical calculations. A large ¹³C isotope effect of ≈1.037 is observed at the tertiary carbon, while small isotope effects are observed at the olefinic carbons. These results support rate-limiting ionization of a η²-Pd complex. The observed isotope effects are compared with predictions from calculational models employing either solvent models or ionization of an amidinium ion. The calculated transition structures are notably η² in character, and the implications of this observation are discussed.     

介孔硅铝酸盐的合成及其在傅克反应中的催化性能

采用溶胶凝胶法合成了一系列有序性好且酸性较强的介孔硅铝酸盐材料。利用X射线粉末衍射(XRD)、透射电镜(TEM)、²⁷Al核磁共振(²⁷Al NMR)、氨气程序升温脱附(HN₃-TPD)及吡啶吸附红外光谱(Py-FT-IR)对制备的介孔硅铝酸盐材料的结构和性能进行表征,并考察了材料在苯甲醚和苯甲醇的傅克烷基化反应中的催化活性。实验结果表明：合成过程中,表面活性剂的用量、硅铝物质的量的比会影响材料结构的有序性,醋酸用量对材料结构有序性影响很小;进一步研究结果表明,n_Si / n_Al比会影响材料的酸催化活性,当n_Si / n_Al=10时材料的酸催化活性最高。氨气程序升温脱附和吡啶吸附红外光谱表明n_Si / n_Al=10的材料含有最多的B酸酸量。