90974-59-7Relevant academic research and scientific papers
A convenient pathway to Sm(ii)-mediated chemistry in acetonitrile
Maisano, Todd,Tempest, Kevin E.,Sadasivam, Dhandapani V.,Flowers II, Robert A.
, p. 1714 - 1716 (2011)
In this communication we show that the instability of samarium diiodide (SmI2) in acetonitrile is a consequence of ionization of the reductant in this solvent. Samarium triflate (Sm(OTf)2) is exceptionally stable in acetonitrile for
Mechanistic Study and Development of Catalytic Reactions of Sm(II)
Maity, Sandeepan,Flowers, Robert A.
, p. 3207 - 3216 (2019/02/19)
Samarium diiodide (SmI2) is one of the most widely used single-electron reductants available to organic chemists because it is effective in reducing and coupling a wide range of functional groups. Despite the broad utility and application of SmI2 in synthesis, the reagent is used in stoichiometric amounts and has a high molecular weight, resulting in a large amount of material being used for reactions requiring one or more equivalents of electrons. Although few approaches to develop catalytic reactions have been designed, they are not widely used or require specialized conditions. As a consequence, general solutions to develop catalytic reactions of Sm(II) remain elusive. Herein, we report mechanistic studies on catalytic reactions of Sm(II) employing a terminal magnesium reductant and trimethylsilyl chloride in concert with a noncoordinating proton donor source. Reactions using this approach permitted reductions with as little as 1 mol % Sm. Mechanistic studies provide strong evidence that during the reaction, SmI2 transforms into SmCl2, therefore broadening the scope of accessible reactions. Furthermore, this mechanistic approach enabled catalysis employing HMPA as a ligand, facilitating the development of catalytic Sm(II) 5-exo-trig ketyl olefin cyclization reactions. The initial work described herein will enable further development of both useful and user-friendly catalytic reactions, a long-standing, but elusive goal in Sm(II) chemistry.
Reversibility of Ketone Reduction by SmI2-Water and Formation of Organosamarium Intermediates
Chciuk, Tesia V.,Anderson, William R.,Flowers, Robert A.
, p. 4579 - 4583 (2017/12/18)
The reduction of ketones by SmI2-water has long been thought to proceed through a reversible initial electron transfer with the formation of organosamarium intermediates in a follow-up step. Kinetic experiments on the reduction of two model ketones and structurally similar ketones with a pendant alkene are shown to be consistent with a rate-limiting reduction by SmI2-water through a proton-coupled electron-transfer (PCET). Literature values for the rates of radical cyclizations and reduction of radicals by SmI2 and thermochemical data for radical reduction by SmI2-water further support a rate-limiting initial step for ketone reductions. These data suggest that discrete organosamarium species may not be intermediates in ketone reductions by SmI2-water.
Secondary amides as hydrogen atom transfer promoters for reactions of samarium diiodide
Chciuk, Tesia V.,Li, Anna M.,Vazquez-Lopez, Andres,Anderson, William R.,Flowers, Robert A.
supporting information, p. 290 - 293 (2017/11/27)
Two secondary amides (N-methylacetamide and 2-pyrrolidinone) were used as additives with SmI2 in THF to estimate the extent of N-H bond weakening upon coordination. Mechanistic and synthetic studies demonstrate significant bond-weakening, providing a reagent system capable of reducing a range of substrates through formal hydrogen atom transfer.
Dynamic ligand exchange in reactions of samarium diiodide
Sadasivam, Dhandapani V.,Teprovich, Joseph A.,Procter, David J.,Flowers II, Robert A.
supporting information; experimental part, p. 4140 - 4143 (2010/11/18)
Mechanistic studies show the importance of iodide displacement by additives that accelerate reactions of samarium diiodide. The key feature important for acceleration of reaction rate is the use of proton donors and other additives that have a high enough affinity for Sm(II) to displace iodide yet do not saturate the coordination sphere inhibiting substrate reduction.
Dibromomethane as one-carbon source in organic synthesis: A versatile methodology to prepare the cyclic and acyclic α-methylene or α-keto acid derivatives from the corresponding terminal alkenes
Hon, Yung-Son,Liu, Yu-Wei,Hsieh, Cheng-Han
, p. 4837 - 4860 (2007/10/03)
Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH2Br2-Et2NH affords α-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A-2 can be easily converted to α-methylene esters A-4, which could be further converted to the corresponding α-keto esters A-5. This methodology can be also applied to the preparation of α-methylene lactones B-4, α-methylene lactams, and α-keto lactones B-5 with various ring sizes.
Development of a method for the reductive cyclization of enones by a titanium catalyst
Kablaoui, Natasha M.,Buchwald, Stephen L.
, p. 3182 - 3191 (2007/10/03)
An effective protocol in which bis(trimethylphosphine)titanocene is used to catalyze the reductive cyclization of enones to cyclopentanols via a metallacyclic intermediate has been developed. The key step in the process is the cleavage of the titanium-oxygen bond in the metallacycle by a silane to regenerate the catalyst. Mechanistic aspects of the reaction are discussed and the diastereoselectivity of the transformation is studied using both achiral and chiral substrates. The scope and limitations of the procedure are described. An in situ protocol for the generation of the air- and moisture-sensitive catalyst has also been developed. This work demonstrates, for the first time, the viability of using an early transition metal complex to catalyze the reductive cyclization of an alkene with a heteroatom-containing functional group.An effective protocol in which bis(trimethylphosphine) titanocene is used to catalyze the reductive cyclization of enones to cyclopentanols via a metallacyclic intermediate has been developed. The key step in the process is the cleavage of the titanium-oxygen bond in the metallacycle by a silane to regenerate the catalyst. Mechanistic aspects of the reaction are discussed and the diastereoselectivity of the transformation is studied using both achiral and chiral substrates. The scope and limitations of the procedure are described. An in situ protocol for the generation of the air-and moisture-sensitive catalyst has also been developed. This work demonstrates, for the first time, the viability of using an early transition metal complex to catalyze the reductive cyclization of an alkene with a heteroatom containing functional group.
