Mechanistic Insights into the Ru(II)-Catalyzed Intramolecular Formal [3 + 2] Cycloaddition of (<i>E</i>)-1,6-Enynes
作者:Rui Liu、Yajie Chou、Bing Lian、De-cai Fang、Ming Gao、Tanyu Cheng、Guohua Liu
DOI:10.1021/acs.orglett.9b02446
日期:2019.9.6
challenge in organic chemistry. Herein, we report a Ru(II)-catalyzed formal [3 + 2] cycloaddition as an efficient method to prepare unprecedented bicyclo[3.3.0]octenes from readily available (E)-1,6-enynes. Mechanistic studies based on the deuterium labeling experiments and the DFT calculation disclose a reasonable mechanistic pathway, where a ruthenacyclopentene generated by an ene-yne oxidative cyclization
The Ni–Pd catalyzed addition–cyclization of sulfanyl 1,6-diynes 2–9 with nucleobases is described. The reactions of N-tethered 1,6-diynes with N3-benzoylthymine, N4,N4-bis(Boc)cytosine, N3-benzoyluracil and N6,N6-bis(Boc)adenine exclusively afforded the pyrrolylmethyl and furylmethyl nucleotides in good yields. Deprotection of nucleobases was completed by treatment with acids or bases. Furthermore
An unconventional sulfur-to-selenium-to-carbon radical transfer: chemo-and regioselective cyclization of yne-ynamides
作者:Shubham Dutta、B. Prabagar、Rajeshwer Vanjari、Vincent Gandon、Akhila K. Sahoo
DOI:10.1039/c9gc03745d
日期:——
regioselective cyclization of yne-tethered-ynamides. Density functional theory studies and HRMS experiments are used to establish a reactivity scale between thiyl and selenyl radicals. The unique features of this transformation include, (1) the chemoselective reactivity of RSe˙ over RS˙, (2) regioselective RSe˙ attack on alkyne over ynamide, (3) 5-exo-dig cyclization of yne-ynamide to unusual 4-selenyl-pyrroles
Developing a Diastereoselective Intramolecular [4 + 3] Cycloaddition of Nitrogen-Stabilized Oxyallyl Cations Derived from <i>N</i>-Sulfonyl-Substituted Allenamides
作者:Andrew G. Lohse、Richard P. Hsung、Mitchell D. Leider、Sunil K. Ghosh
DOI:10.1021/jo200147h
日期:2011.5.6
Efforts toward achieving a practical and diastereoselective intramolecular [4 + 3] cycloaddition of nitrogen-stabilizedoxyallylcations with tethered dienes are described. Epoxidation of N-sulfonyl substituted allenamides with dimethyldioxirane (DMDO) generates nitrogen-stabilizedoxyallylcations that readily undergo stereoselective [4 + 3] cycloaddition with dienes. Selectivity is found to depend
Copper-Catalyzed Domino Homologation and Cycloisomerization Reactions for 3-Pyrroline Synthesis
作者:Ye Ho Shin、Muchchintala Maheswara、Joon Young Hwang、Eun Joo Kang
DOI:10.1002/ejoc.201301621
日期:2014.4
catalyst for a dominoreaction sequence leading to 3-pyrrolines. The Cu(I)-catalyzed Crabbe reaction of propargyl sulfonamide and selective cycloisomerization of the allene intermediate were carried out using microwave irradiation conditions affording a wide range of 2-substituted- and 2,5-disubstituted-3-pyrrolines. Mechanistic studies of the reaction intermediates revealed two possible reaction pathways;