Selective Synthesis of 5- or 6-Aryl Octahydrocyclopenta[b]pyrroles from a Common Precursor through Control of Competing Pathways in a Pd-Catalyzed Reaction
摘要:
The Pd/phosphine-catalyzed reaction of 1 with aryl bromides leads to the selective synthesis of either 6-aryl octahydrocyclopenta[b]pyrroles (3), the corresponding 5-aryl isomers 5, diarylamine 2, or hexahydrocyclopenta[b]pyrrole 4 depending on the structure of the phosphine ligand. These transformations are effective with a variety of different aryl bromides and provide 3-5 with excellent levels of diastereo-selectivity (dr >= 20:1). The changes in product distribution are believed to derive from the influence of Pd-catalyst structure on the relative rates of reductive elimination, beta-hydride elimination, alkene insertion, and alkene displacement processes in a mechanistically complex reaction. The effect of phosphine ligand structure on product distribution is described in detail, along with analysis of a proposed mechanism for these transformations.
Iodine(V) Reagents in Organic Synthesis. Part 3. New Routes to Heterocyclic Compounds via <i>o</i>-Iodoxybenzoic Acid-Mediated Cyclizations: Generality, Scope, and Mechanism
作者:K. C. Nicolaou、P. S. Baran、Y.-L. Zhong、S. Barluenga、K. W. Hunt、R. Kranich、J. A. Vega
DOI:10.1021/ja012126h
日期:2002.3.1
The discovery and development of the o-iodoxybenzoic acid (IBX) reaction with certain unsaturated N-aryl amides (anilides) to form heterocycles are described. The application of the method to the synthesis of delta-lactams, cyclic urethanes, hydroxy amines, and amino sugars among other important building blocks and intermediates is detailed. In addition to the generality and scope of this cyclization
of nitrogen‐centered radicals, generated through electrochemical oxidation, to alkenes followed by trapping of the cyclized radical intermediate with 2,2,6,6‐tetramethylpiperidine‐N‐oxyl radical (TEMPO). Difunctionalization of a variety of alkenes with easily available carbamates/amides and TEMPO affords aminooxygenation products in high yields and with excellent trans selectivity for cyclic systems
作者:Shuai Zheng、Shuo-Qing Zhang、Borna Saeednia、Jiawang Zhou、Jessica M. Anna、Xin Hong、Gary A. Molander
DOI:10.1039/d0sc01459a
日期:——
The selective 1,2-aminoacylation of olefins provides opportunities for the rapid construction of nitrogen-containing molecules. However, the lack of CO-free acylation reactions has limited their application. By using photoredox proton-coupled electron transfer (PCET)/Ni dual-catalysis, a highly regio- and diastereoselective amidoacylation of unactivated olefins has been developed. Various acyl electrophiles
Palladium-Catalyzed Vinylation of Cyclopentenes with Inverted <i>Z,E</i>-Isomerism of Vinylic Substrates
作者:Chao-Ting Yen、Yi-Hung Liu、Shie-Ming Peng、Shiuh-Tzung Liu
DOI:10.1021/acs.orglett.2c01131
日期:2022.5.13
efficiently produce the coupled vinyl cyclopentenes with excellent regio- and stereoselectivity is reported. Typically, a Pd-catalyzed reaction of 2-(cyclopent-2-en-1-yl)-N-tosylacetamide (1a) with (E)-styryl bromides gave cis-2-((Z)-styryl)cyclopent-3-en-1-yl-N-tosylacetamide (3e), an allylic substitution product. Interestingly, we have found that the E,Z-stereochemistry of vinylic substrates is inverted in
报道了一种钯促进的 Mizoroki-Heck 型反应,该反应采用导向基团策略有效地生产具有优异区域和立体选择性的偶联乙烯基环戊烯。通常,Pd 催化的 2-(cyclopent-2-en-1-yl) -N - tosylacetamide ( 1a ) 与 ( E )-styryl bromides 的反应得到cis -2-((( Z )-styryl)cyclopent-3 -en-1- yl- N - tosylacetamide ( 3e ),一种烯丙基取代产物。有趣的是,我们发现乙烯基底物的E、Z立体化学在这些产品中是相反的。讨论了这种催化反应的机理。
Chemoselective bond activation by unidirectional and asynchronous PCET using ketone photoredox catalysts
作者:Rui Sun、Serge Ruccolo、Daniel L. Nascimento、Yangzhong Qin、Nathaniel Hibbert、Daniel G. Nocera
DOI:10.1039/d3sc04362b
日期:——
The tripletexcited states of ketones are found to effect selective H-atom abstraction from strong amide N–H bonds in the presence of weaker C–H bonds through a proton-coupled electron transfer (PCET) pathway. This chemoselectivity, which results from differences in ionization energies (IEs) between functional groups rather than bond dissociation energies (BDEs) arises from the asynchronicity between