Allenes bearing a nucleophilic group cyclize on treatment with acyltetracarbonyl cobalt complexes in the presence of mild bases. Various nucleophilic groups and cobalt complexes can be used to give highly functionalized pyrrolidines, cyclopentanes and tetrahydrofurans. Disubstituted allenes may be used in the reaction. 1,3-disubstituted allenes give products with high stereoselectivity.
Palladium(II)-Catalyzed Tandem Reaction of Intramolecular Aminopalladation of Allenyl <i>N</i>-Tosylcarbamates and Conjugate Addition
作者:Guosheng Liu、Xiyan Lu
DOI:10.1021/ol016727p
日期:2001.11.1
A divalent palladium-catalyzed tandem cyclization-coupling reaction of allenyl N-tosylcarbamates and acrolein was developed. The reaction gave aldehyde-functionalized 2-oxazolidinones in one step with high regioselectivity. A mechanism involving intramolecular aminopalladation of allene, followed by insertion of alkene and C-Pd bond protonolysis, is proposed. [reaction: see text]
Palladium(II)-catalyzed coupling of allenoic acids and α,β-unsaturated carbonyl compounds through tandem intramolecular oxypalladation and conjugate addition reactions
作者:Guosheng Liu、Xiyan Lu
DOI:10.1016/s0040-4039(02)02507-8
日期:2003.1
A regioselective divalent palladium-catalyzed tandem coupling reaction of allenoic acids with α,β-unsaturated carbonylcompounds was developed. The reaction involves intramolecular oxypalladation of an allene, followed by insertion of the α,β-unsaturated carbonylcompound and protonolysis of the CPd bond to regenerate the Pd(II) species in the presence of excess halide ions. Functionalized lactones
Cp<sub>2</sub>ZrCl<sub>2</sub>-Mediated Three-Component Coupling Reactions of CO<sub>2</sub>, Ethylene (or Alkynes), and Electrophiles Leading to Carboxylic Acid Derivatives
作者:Naoto Chatani、Kohei Yamashita
DOI:10.1055/s-2005-864807
日期:——
pressure of CO 2 . The treatment of Cp 2 ZrCl 2 with EtMgBr followed by exposure to CO 2 generates zirconacycle 1, which can react with various electrophiles to give a variety of carboxylic acid derivatives. Unsaturated zircona-cycles 2 can also generated from Cp 2 ZrCl 2 , EtMgBr, alkynes, and CO 2 . Complexes 2 react with electrophiles to give α,β-unsaturated acids stereoselectively.
Regioselective Intramolecular Allene Amidation Enabled by an EDA Complex**
作者:Lu Liu、Robert M. Ward、Jennifer M. Schomaker
DOI:10.1002/chem.202002533
日期:2020.11.2
The addition of radicals to unsaturated precursors is a powerful tool for the synthesis of both carbo‐ and heterocyclic organic building blocks. The recent advent of mild ways to generate N‐centered radicals has reignited interest in exploiting highly regio‐, chemo‐, and stereoselective transformations that employ these reactive intermediates. While the additions of aminyl, iminyl, and amidyl radicals
heteroatomic group (hydroxy, alcoxy, halogen, dialkylamino) or a phenyl in the γ position exhibits a strong peak corresponding to the loss of C2H4 (28a.m.u.) from the molecular ion. This is commonly the base peak of the spectra and due to a McLafferty type transfer of the heteroatom or phenyl group to the central allenic carbonatom. The methylgroup shows a lower migratory aptitude in such a process. This
被在γ位上带有杂原子基团(羟基,烷氧基,卤素,二烷基氨基)或苯基的烃链取代的烯丙基化合物的质谱表现出与C 2 H 4损失相对应的强峰(28a.mu)来自分子离子。这通常是光谱的基峰,这是由于杂原子或苯基基团向中心烯丙碳原子的麦克拉费蒂型转移。在这种过程中,甲基显示出较低的迁移能力。在γ-卤素和γ-羟基酮,烯烃,炔烃或芳烃的光谱中未观察到涉及杂原子基团迁移的这种类型的断裂,并且似乎是烯丙基键的特征。提出了杂原子基团(或苯基)对中心烯丙基碳原子的亲核攻击。