A New Platinum Complex Catalyzed Reaction Involving Nucleophilic Substitution at the Central Carbon Atom of the π-Allyl Ligand
摘要:
The reaction of 2-chloro-allyl acetate with sodium ethyl acetoacetate in the presence of a platinum(O) complex gave furan derivatives. The key feature of this-new platinum-catalyzed reaction is the nucleophilic substitution at the central carbon atom of pi-allyl complexes. The regioselectivity of the nucleophilic attacks (central or terminal) is dependent on the pK(a) of the nucleophile. In addition, a labeling experiment revealed that a rapid syn-anti isomerization of the (pi-allyl) platinum complexes occurs.
Visible Light‐Enabled sp
<sup>3</sup>
‐C−H Functionalization with Chloro‐ and Bromoalkynes: Chemoselective Route to Vinylchlorides or Alkynes
作者:Tapas Adak、Marvin Hoffmann、Sina Witzel、Matthias Rudolph、Andreas Dreuw、A. Stephen K. Hashmi
DOI:10.1002/chem.202001259
日期:2020.12
valuable vinyl chlorides. The photo‐organocatalytic hydrogen atom transfer strategy gives rise to a broad range of diversely functionalized olefins. When bromoalkynes are applied in the presence of a base, a chemoselectivity switch to an alkynylation is observed. This reaction can even be performed for the alkynylation of unactivated sp3‐C−H bonds, in this case with a preference of the more substituted
实现了氯炔的前所未有的直接原子经济化学和区域选择性加氢烷基化和溴炔的 sp 3 -C-H 炔基化。反应伙伴是未官能化的醚、醇、酰胺,甚至未活化的烃。我们发现家用荧光灯能够激发二芳基酮,然后二芳基酮选择性地从 sp 3 ‐C−H 键中提取 H 原子。用氯炔获得正式炔插入 sp 3 ‐C−H 键的产物,从而提供有价值的氯乙烯。光有机催化氢原子转移策略产生了多种不同官能化的烯烃。当在碱存在下应用溴代炔时,观察到化学选择性转变为炔基化。该反应甚至可以用于未活化的 sp 3 -C-H 键的炔基化,在这种情况下优选取代更多的碳。伴随的量子化学计算表明乙烯基自由基中间体与碳自由基中心具有明显的线性配位,从而能够在H原子抽象后形成两种非对映异构体,表明( Z )-非对映异构体是优选的,这支持了实验观察到的( E / Z )‐分布。
Reactions of α-Functionally Substituted Enals with Terminal Alkynes: Unexpected Assembly of 2-Amino-2-Cyclopentenones
作者:Rustam B. Shnigirev、Igor A. Ushakov、Valentin A. Semenov、Alexander Yu. Rulev
DOI:10.1021/acs.joc.3c00340
日期:——
α-amino functionally substituted enals with terminal alkynes leading either to corresponding propargyl alcohols (for O-, S-, Cl-, and Br-bearing substrates) or unexpected 2-amino-2-cyclopentenones (for aminoenals) are described. The key feature of these reactions is the rearrangement of adducts bearing amino groups on silica gel that triggered further cyclization to five-membered carbocycles.
We present the first productive ring-closing metathesis reaction that leads to the construction of cyclic alkenyl bromides. Efficient catalysis employing commercially available Grubbs II catalyst is possible through appropriate modification of the starting bromoalkene moiety.
Chromium Vinylidene Carbenoids: Stereospecific Synthesis of (<i>Z</i>)-2-Chloroalk-2-en-1-ols
作者:D. K. Barma、Rachid Baati、Alain Valleix、Charles Mioskowski、J. R. Falck
DOI:10.1021/ol016935h
日期:2001.12.1
[GRAPHICS](Z)-2-Chloroalk-2-en-1-ols are obtained in excellent yields from a wide variety of aldehydes by addition of (E)-chromium vinylidene carbenoids, stereospecifically generated from trichloroalkanes using CrCl2 in THF at room temperature.
CHIN, CHONG SHIK;LEE, BYEONGUO;PARK, SUNG CHUL, J. ORGANOMET. CHEM., 393,(1990) N, C. 131-135