120790-38-7Relevant academic research and scientific papers
Ligand, Solvent, and Deuterium Isotope Effects in Mn(III)-Based Oxidative Free-Radical Cyclizations
Snider, Barry B.,McCarthy, Bridget A.
, p. 6217 - 6223 (2007/10/02)
Oxidation of β-keto ester 1 with Mn(pic)3 and Cu(OAc)2 affords bicycloalkane 8, not the expected alkene 7, which is formed in high yield with Mn(OAc)3 and Cu(OAc)2.A series of control experiments established that the most likely explanation for this observation is that Mn(pic)2, but not Mn(OAc)2, reacts with the bicyclic radical 5 more rapidly than Cu(OAc)2 does.These studies also indicate the potential for improved yields from oxidative free-radical cyclization of deuterated substrates.For instance, reaction of β-keto ester 1-d with 2 equiv of Mn(OAc)3 and no Cu(OAc)2 affords 65percent of 8, whereas β-keto ester 1 provides only 22percent of 8 under the same conditions.Large kinetic isotope effects change the nature of the termination step and prevent the formation of acyclic radical 3 by intermolecular hydrogen transfer.Solvent and ligand effects on the oxidation of β-keto ester 1, malonate 14, and acetylenic β-keto ester 25 are described.
Cerium (IV) ammonium nitrate promoted oxidative cyclization of dimethyl 4-pentenylmalonate
Baciocchi,Paolobelli,Ruzziconi
, p. 4617 - 4622 (2007/10/02)
CAN promoted oxidative cyclization of dimethyl 4-pentenylmalonate has been investigated in MeOH and in AcOH. The product distribution and the regioselectivity of the reaction (5-exo/6-endo ratio) appear to be very sensitive to the reaction conditions as w
Solvent Effects on Manganese(III)-Based Oxidative Free-Radical Cyclizations: Ethanol and Acetic Acid
Snider, Barry B.,Merritt, John E.,Dombroski, Mark A.,Buckman, Brad O.
, p. 5544 - 5553 (2007/10/02)
Ethanol complements the typical solvent, acetic acid, for Mn(III)-based oxidative free-radical cyclizations.Cyclization of enol ether 1c to give gibberellic acid intermediate 6c is successfull in ethanol, but not in acetic acid.Ethanol acts as a reducing
Atom Transfer Cyclization Reactions of α-Iodo Esters, Ketones, and Malonates: Examples of Selective 5-Exo, 6-Endo, 6-Exo, and 7-Endo Ring Closures
Curran, Dennis P.,Chang, Chi-Tai
, p. 3140 - 3157 (2007/10/02)
The preparation and free-radical cyclization reactions of unsaturated α-iodo esters, ketones, and malonates have been investigated.For example, sunlamp irradiation of methyl 2-iodo-6-heptenoate in benzene in the presence of 10 mol percent hexabutylditin produces methyl 2-(iodomethyl)cyclopentanecarboxylate (cis and trans) and methyl 3-iodocyclohexanecarboxylate in a ratio of 93/7 in a combined yield of 86percent.The γ-iodo carbonyl products can either be isolated (in most cases) or converted in situ to deiodinated products (with Bu3SnH) or lactones (by heating).Five-, six-, or seven-membered rings selectively form, depending on chain length and alkene substitution.Terminal alkene substituents favor exo cyclization while internal alkene substituents promote endo cyclization.A preference for endo closure is also observed when there is a carbonyl group "inside" the forming ring.A detailed analysis of reaction rates indicates that these isomerizations proceed by an iodine atom transfer chain mechanism, and thus the observed selectivities are due to the kinetic substituent effects.The results contrast the thermodynamically controlled hydrogen atom transfer cyclizations of Julia.A new procedure for the removal of tin byproducts is described.
