73604-43-0Relevant academic research and scientific papers
Efficient regio- And stereoselective formation of azocan-2-ones via 8-endo cyclization of α-carbamoyl radicals
Fang, Xinqiang,Liu, Kun,Li, Chaozhong
, p. 2274 - 2283 (2010)
The iodine-atom-transfer 8-endo cyclization of α-carbamoyl radicals was investigated experimentally and theoretically. With the aid of Mg(CIO 4)2 and a bis(oxazoline) ligand, N- ethoxycarbonylsubstituted N-(pent-4-enyl)-2-iodoalkanamides underwent 8-endo cyclization leading to the formation of only the corresponding 3,5-trans-substituted azocan-2-ones in excellent yields. Similarly, the BF 3·OEt2/H2O-promoted reactions of N-ethoxycarbonyl-N-(2-allylaryl)-2-iodoalkanamides afforded exclusively the benzazocanone products with a 3,5-cis configuration in high yields. The bidentate chelation of substrate radicals not only significantly improved the efficiency of cyclization but also resulted in the change of stereochemistry of azocanone products from 3,8-iransto 3,8-cis. Theoretical calculations at the UB3LYP/6-31G* level revealed that the cyclization of N-carbonyl- substituted α-carbamoyl radicals occurs via the E-conformational transition states without the presence of a Lewis acid. On the other hand, the cyclization proceeds via the Z-conformational transition states when the substrates form the bidentate chelation with a Lewis acid. In both cases, the 8-endo cyclization is always fundamentally preferred over the corresponding 7-exo cyclization. The complexed radicals having the more rigid conformations also allow the better stereochemical control in the iodine-atom-abstraction step. To further understand the reactivity of a-carbamoyl radicals, the competition between the 8-endo and 5-exo cyclization was also studied. The results demonstrated that the 8-endo cyclization is of comparable rate to the corresponding 5-exo cyclization for a-carbamoyl radicals with fixed Z-conformational transition states. As a comparison, the 8-endo mode is fundamentally preferred over the 5-exo mode in the cyclization of NH-amide substrates because the latter requires the Z-conformational transition states, whereas the former proceeds via the more stable E-conformational transition states.
Stereoselectivity in amidyl radical cyclisations: Alkyl mode cyclisations
Clark, Andrew J.,Deeth, Robert J.,Samuel, Christopher J.,Wongtap, Hathaichanuk
, p. 444 - 446 (1999)
Amidyl radicals 2 generated from tributylstannane mediated homolysis of O-benzoyl hydroxamic acid derivatives 6a-g undergo alkyl mode 5-exo cyclisation to give mixtures of cis and trans N-acyl pyrrolidinones (d.e. = 54-74%). The efficiency of the process
Chelating diamide based rate enhancement of intramolecular alkene hydroaminations catalyzed by a neutral Sc(III) complex
Joon, Young Kim,Livinghouse, Tom
, p. 4391 - 4393 (2007/10/03)
(Chemical Equation Presented) Neutral scandium amido complexes are viable catalysts for intramolecular alkene hydroamination. Catalytic activity is strongly coupled to the electronic character of the Sc(III) ligand environment with chelating diamide coord
