56907-39-2Relevant articles and documents
Titanocene(III)-Catalyzed Precision Deuteration of Epoxides
Gans?uer, Andreas,H?thker, Sebastian,Henriques, Dina Schwarz G.,Klare, Sven,Mika, Regine,Rojo-Wiechel, Elena,Schacht, Jonathan H.,Schmickler, Niklas
supporting information, (2021/12/24)
We describe a titanocene(III)-catalyzed deuterosilylation of epoxides that provides β-deuterated anti-Markovnikov alcohols with excellent D-incorporation, in high yield, and often excellent diastereoselectivity after desilylation. The key to the success of the reaction is a novel activation method of Cp2TiCl2 and (tBuC5H4)2TiCl2 with BnMgBr and PhSiD3 to provide [(RC5H4)2Ti(III)D] without isotope scrambling. It was developed after discovering an off-cycle scrambling with the previously described method. Our precision deuteration can be applied to the synthesis of drug precursors and highlights the power of combining radical chemistry with organometallic catalysis.
PICOLINAMIDES AS FUNGICIDES
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Paragraph 0077; 0078, (2019/09/20)
This disclosure relates to picolinamides of Formula I and their use as fungicides.
Dynamic Reductive Kinetic Resolution of Benzyl Ketones using Alcohol Dehydrogenases and Anion Exchange Resins
Méndez-Sánchez, Daniel,Mangas-Sánchez, Juan,Busto, Eduardo,Gotor, Vicente,Gotor-Fernández, Vicente
, p. 122 - 131 (2016/01/25)
Dynamic reductive kinetic resolutions of racemic 3-arylalkanones have been performed by the proper combination of an alcohol dehydrogenase and a basic anionic resin. The best results were found for the bioreduction with the alcohol dehydrogenase type A from Rhodococcus ruber DSM 44541 overexpressed in Escherichia coli (E. coli/ADH-A) and the commercially available evo-1.1.200, while the Amberlite IRA-440 C and the DOWEX-MWA-1 resins allowed efficient in situ racemizations. Reaction conditions were optimized in terms of enzyme source and loading, type and amount of resin, pH, temperature and reaction times, obtaining a series of (R,R)-substituted propan-2-ols with good conversions and both diastereoselectivity and stereoselectivity. As a proof of concept, the subsequent intramolecular cyclization of a selected propan-2-ol substrate afforded a valuable isochroman heterocycle without any loss of the optical purity.
Catalytic hydrogen atom transfer (HAT) for sustainable and diastereoselective radical reduction
Gansaeuer, Andreas,Klatte, Max,Braendle, Gerhard M.,Friedrich, Joachim
, p. 8891 - 8894 (2012/10/08)
Going cyclic! A catalytic cycle and cyclic transition states enable a novel sustainable and catalytic hydrogen atom transfer (HAT) for highly diastereoselective radical reductions. Readily available nontoxic silanes are the terminal reductants for epoxides that are opened by bifunctional titanocene(III) hydride catalysts. Copyright
Screening on the use of Kluyveromyces marxianus CBS 6556 growing cells as enantioselective biocatalysts for ketone reductions
Vitale, Paola,Perna, Filippo Maria,Perrone, Maria Grazia,Scilimati, Antonio
body text, p. 1985 - 1993 (2012/03/22)
The versatility of Kluyveromyces marxianus CBS 6556 growing cells in the enantioselective reduction of ketone functionalities to the corresponding alcohols was exploited. In particular, methyl ketones were reduced to (S)-alcohols with ees of up to 96%. Longer chain alkyl ketones afforded, under the same experimental condition, (R)-alcohols with an ee of up to 84%. Interestingly, carbon-carbon double and the triple bonds can also be reduced in the presence of Kluyveromyces marxianus CBS 6556 yeast. A cyclic ketone, such as 2-tetralone, was also quantitatively reduced to its corresponding (S)-alcohol with ee = 76%.
Copper-catalyzed diboration of ketones: Facile synthesis of tertiary α-Hydroxyboronate esters
McIntosh, Melissa L.,Moore, Cameron M.,Clark, Timothy B.
supporting information; experimental part, p. 1996 - 1999 (2010/07/17)
Figure presented The diboration of ketones with the (ICy)CuOt-Bu catalyst was developed to provide access to tertiary α-hydroxyboronate esters. The (ICy)CuOt-Bu catalyst was generated in situ with (ICy)CuCl and NaOt-Bu to afford a more efficient catalyst than the preformed (ICy)CuOt-Bu. These conditions result in the diboration of various ketones in toluene at 50 °C in 2-22 h. Treatment of the resulting products with silica gel affords the corresponding α-hydroxyboronate esters.
Stereoselective addition of organomanganese reagents to chiral acylsilanes and aldehydes
Boucley, Céline,Cahiez, Gérard,Carini, Silvia,Cerè, Vanda,Comes-Franchini, Mauro,Knochel, Paul,Pollicino, Salvatore,Ricci, Alfredo
, p. 223 - 228 (2007/10/03)
Organomanganese halides and organomanganates prepared by transmetalation of organolithium and Grignard reagents add smoothly to the carbonyl moiety of acylsilanes and of substituted aldehydes bearing a chiral center at the α-position affording the desired
Samarium diiodide-promoted diiodomethylation of carbonyl compounds with iodoform. Synthetic applications of diiodoalcohols
Concellon, Jose M.,Bernad, Pablo L.,Perez-Andres, Juan A.
, p. 1409 - 1412 (2007/10/03)
A rapid and effective diiodomethylation of carbonyl compounds using SmI2 and iodoform is described. Transformations of the obtained diiodoalcohols 2 into α-iodoaldehydes 5 and α-hydroxyacids 6 is also reported.
The importance of conformational effects on the carbon-carbon bond cleavage of β-phenethyl ether radical cations
Perrott,De Lijser,Arnold
, p. 384 - 397 (2007/10/03)
The photosensitized (electron transfer) bond cleavage of some β-phenylethyl ether radical cations has been investigated. In previous studies the feasibility of the bond cleavage was thought to depend on the bond dissociation energy (BDE). However, this simple hypothesis led to several incorrect predictions and therefore additional criteria, conformational effects, were added to the hypothesis. This study has now been extended and additional examples of the importance of the conformation on the carbon-carbon bond cleavage of radical cations are provided. The four β-phenylethyl ethers studied are 2-methoxy-3-phenylbutane (9, both diastereomers), and cis- and trans-2-methyl-3-phenyltetrahydropyran (10c, 10t). Generally, bond cleavage will occur if the (calculated) BDE in the radical cation is less than 55 kJ/mol, and if there is significant overlap between the singly occupied molecular orbital (SOMO) and the vulnerable (C - C or C - H) bond. In the case of a β-phenylethyl ether radical cation, the alkoxy group must also be oriented so that an oxygen lone pair of electrons can overlap with the C - C sigma antibonding (σ*) orbital. The calculated BDE values of the vulnerable C - C bond in the radical cations of the four ethers studied here are well below the threshold value, 55 kJ/mol, and C - C cleavage will therefore be governed by conformational effects. Molecular mechanics (MM3) calculations were used to identify the most stable conformers of the neutral molecules. Based on the calculated angles and overlap between orbitals it was predicted that the global-minimum conformers of the ethers 9 and 10c would not give C - C bond cleavage products or deprotonation to any significant extent. The global minimum of ether 10t is well oriented for C - C cleavage but not for deprotonation. Irradiation of an electron-accepting photosensitizer, 1,4-dicyanobenzene (2), in the presence of the ethers showed that the ethers 9 did not cleave efficiently; no deprotonation or isomerization was observed. This is in good agreement with the predictions based on the MM3 calculations. Both ethers 10c and 10t gave reasonable yields of the C - C cleavage products; in fact, ether 10c cleaved more efficiently than 10t. This can be explained by the fact that a conformer of 10c, only 4.35 kJ/mol higher in energy than the global minimum, is perfectly aligned for cleavage. Ether 10t did not show any evidence for deprotonation whereas 10c did. This is also in good agreement with the calculations.
A Convenient Procedure for the Reduction of Esters, Carboxylic Acids, Ketones and Aldehydes using Tetrabutylammonium Fluoride (or Triton B) and Polymethylhydrosiloxane
Drew, Mark D.,Lawrence, Nicholas J.,Fontaine, David,Sehkri, Lakhdar,Bowles, Stephen A.,Watson, William
, p. 989 - 991 (2007/10/03)
A range of carboxylic esters and acids have been converted efficiently to the corresponding alcohols with polymethylhydrosiloxane in the presence of catalytic tetrabutylammonium fluoride. The reduction of ketones and aldehydes with PMHS and other alkoxysilanes in the presence of TBAF or benzyltrimethylammonium hydroxide is also described.
