Instantaneous SmI₂/H₂O/Amine‐Mediated Reductions in THF

Abstract

The SmI(2)-mediated reductions of ketones, imines, and alpha,beta-unsaturated esters have been shown to be instantaneous in the presence of H(2)O and an amine in THF. The SmI(2)-mediated reductions are not only shown to be fast and quantitative by the addition of H(2)O and an amine, but the workup procedures are also simplified. Competing experiments with SmI(2)/H(2)O/amine confirmed that alpha,beta-unsaturated esters could be selectively reduced in the presence of ketones or imines. Comparison of analogue ligands showed that nitrogen and phosphorus ligands are superior to oxygen and sulfur ligands in these reductions. The trialkylphosphine 1,2-bis(dimethylphosphino)ethane (DMPE) provided a primary kinetic isotope effect, yielding a k(H)/k(D) of 4.5.

Samarium(II) Iodide Mediated Reductions − Influence of Various Additives

“…The driving force for the reaction has been suggested to be the precipitation of the by-products. [14] When conjugated double and triple bonds were found to be rapidly reduced to simple alkenes or alkanes, it was concluded that the SmI 2 /H 2 O/amine mixture is a very powerful reductant (Scheme 17). [50] Scheme 17.…”

“…[14] The less sterically crowded 4-phenyl-2-butanone was reduced approximately 130 times faster than 2-methyl-3-heptanone with the reagent mixture SmI 2 /diglycol.…”

“…reactions were complete in less than 10 seconds. [14] The SmI 2 /H 2 O/amine mixture is particularly useful for the reductive imino-pinacol coupling of hindered imines and iminium perchlorates, since these are difficult to couple by other methods. [49] UV/Vis studies have revealed that water is a very good ligand for samarium(), i.e.…”

Synthesis, crystal structure, and chirality of divalent lanthanide reagents containing tri- and tetraglyme

“…Divalent lanthanide complexes can function as oneelectron reductants, and especially samarium(II) complexes such as [SmI 2 (thf) 5 ] [1], [SmI 2 (hmpa) 4 ] [2], and [Sm(hmpa) 6 ]I 2 [3] have found extensive use as mild and selective reducing agents [4][5][6][7][8][9][10][11][12][13]. With the long-term goal of mastering the design and synthesis of enantioselective reducing agents, we have embarked on an exploratory synthesis project.…”

Highly Oxygenated Diterpenoids Associated to the Central Nervous System: Syntheses of Salvinorin and Forskolin

“…23 Careful tuning of reaction conditions revealed that freshly prepared samarium diiodide furnished lactonic ester 57 in the presence of triethylamine 24 as a ligand and acetic acid as a proton source in toluene as a single diastereomer. When the reaction was quenched by oxygen bubbling, recovery of the product was improved by minimizing side reactions with excess samarium diiodide.…”