| 1. |
- Ankner, Tobias, 1976, et al.
(författare)
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KHMDS enhanced SmI(2)-mediated reformatsky type alpha-cyanation.
- 2010
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Ingår i: Organic letters. - : American Chemical Society (ACS). - 1523-7052 .- 1523-7060. ; 12:10, s. 2210-3
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Tidskriftsartikel (refereegranskat)abstract
- A novel combination of SmI(2), KHMDS, and TsCN can be utilized to introduce a cyano group into structurally diverse and highly sensitive 2-alkyl-chroman-4-ones. Subsequent oxidation allows the formed 2-alkyl-3-cyanochromones to be isolated in yields ranging from 49 to 77%. In addition, alpha-bromoketones and esters were found to undergo equally effective alpha-cyanation.
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| 2. |
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| 3. |
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| 4. |
- Ankner, Tobias, 1976, et al.
(författare)
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Selective cleavage of 3,5-bis-(trifluoromethyl)benzylcarbamate by SmI2-Et3N-H2O
- 2013
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 49:61, s. 6867-6869
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Tidskriftsartikel (refereegranskat)abstract
- A novel electron poor protection group for amines has been developed. It undergoes rapid cleavage by SmI2-Et3N-H2O and its orthogonality towards the regular benzyl carbamate group (CBz) under reductive or transfer hydrogenolytic conditions is reported.
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| 6. |
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| 7. |
- Chciuk, T. V., et al.
(författare)
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Solvent-Dependent Substrate Reduction by (Sm N(SiMe3)(2) (2)(THF)(2)}. An Alternative Approach for Accelerating the Rate of Substrate Reduction by Sm(II)
- 2014
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 79:20, s. 9441-9443
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Tidskriftsartikel (refereegranskat)abstract
- The impact of solvent on electron transfer from Sm(II) to substrates was measured by determining the rate of reduction of 1-bromo-, 1-chlorododecane, and 3-pentanone in THF and hexanes using the highly soluble reductant {Sm[N(SiMe3)(2)](2)(THF)(2)}. Rates were found to be 3 orders of magnitude faster in hexanes than THF, and reductions of alkyl halides were inverse first order in THF. These findings show the solvent milieu significantly impacts the rate of substrate reduction, a consideration that may prove useful in synthesis.
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| 8. |
- Dahlén, Anders, 1977, et al.
(författare)
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Estimating the limiting reducing power of SmI2/H2O/amine and YbI2/H2O/amine by efficient reduction of unsaturated hydrocarbons.
- 2006
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Ingår i: The Journal of organic chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 71:4, s. 1576-80
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Tidskriftsartikel (refereegranskat)abstract
- The mixture of samarium diiodide, amine, and water (SmI2/H2O/Et3N) is known to be a particularly powerful reductant, but until now the limiting reducing power has not been determined. A series of unsaturated hydrocarbons with varying half-wave reduction potentials (E(1/2) = -1.6 to -3.4 V, vs SCE) have been treated with SmI2/H2O/Et3N and YbI2/H2O/Et3N, respectively. All hydrocarbons with potentials of -2.8 V or more positive were readily reduced with SmI2/H2O/Et3N, whereas all hydrocarbons with potentials of -2.3 V or more positive were readily reduced using YbI2/H2O/Et3N. This defines limiting values of the chemical reducing power of SmI2/H2O/Et3N to -2.8 V and of YbI2/H2O/Et3N to -2.3 V vs SCE.
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| 9. |
- Dahlén, Anders, 1977, et al.
(författare)
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Exploring SmBr2-, SmI2-, and YbI2-mediated reactions assisted by microwave irradiation.
- 2005
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Ingår i: Chemistry (Weinheim an der Bergstrasse, Germany). - : Wiley. - 0947-6539. ; 11:11, s. 3279-84
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Tidskriftsartikel (refereegranskat)abstract
- The use of microwave heating in lanthanide(II) halide (LnX2 = SmBr2, SmI2, and YbI2) mediated reduction and coupling reactions has been investigated for a variety of functional groups including alpha,beta-unsaturated esters, aldehydes, ketones, imines, and alkyl halides. Good to quantitative transformations were obtained within a few minutes without the addition of any co-solvents, such as hexamethyl phosphoramide (HMPA). The redox potential of YbI2 in tetrahydrofuran (THF) has been determined as -1.02+/-0.05 V (versus Ag/AgNO3) by cyclic voltammetry. A large selectivity difference in various reactions was observed depending on the redox potential of the LnX2 reagent. The more powerful reductant, SmBr2, afforded mainly pinacol-coupling products of ketones whereas the weaker reductant YbI2 afforded mainly reduction products. The results indicate that the reducing power of LnX2 has a large impact on not only the pinacol coupling/reduction product ratio of ketones but also on other substrates in which there are competing coupling and reduction reactions. The use of in situ generated LnX2 has also been explored and proven useful in many of these reactions.
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| 10. |
- Dahlén, Anders, 1977, et al.
(författare)
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Mechanistic study of the SmI2/H2O/amine-mediated reduction of alkyl halides: amine base strength (pKBH+) dependent rate.
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 127:23, s. 8340-7
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics of the SmI(2)/H(2)O/amine-mediated reduction of 1-chlorodecane has been studied in detail. The rate of reaction is first order in amine and 1-chlorodecane, second order in SmI(2), and zero order in H(2)O. Initial rate studies of more than 20 different amines show a correlation between the base strength (pK(BH+) of the amine and the logarithm of the observed initial rate, in agreement with Bronsted catalysis rate law. To obtain the activation parameters, the rate constant for the reduction was determined at different temperatures (0 to +40 degrees C, DeltaH++ = 32.4 +/- 0.8 kJ mol(-1), DeltaS++ = -148 +/- 1 J K(-1) mol(-1), and DeltaG++(298K) = 76.4 +/- 1.2 kJ mol(-1)). Additionally, the (13)C kinetic isotope effects (KIE) were determined for the reduction of 1-iododecane and 1-bromodecane. Primary (13)C KIEs (k(12)/k(13), 20 degrees C) of 1.037 +/- 0.007 and 1.062 +/- 0.015, respectively, were determined for these reductions. This shows that cleavage of the carbon-halide bond occurs in the rate-determining step. A mechanism of the SmI(2)/H(2)O/amine-mediated reduction of alkyl halides is proposed on the basis of these results.
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