3347-57-7Relevant academic research and scientific papers
Enantioselective Radical Carbocyanation of 1,3-Dienes via Photocatalytic Generation of Allylcopper Complexes
Lu, Fu-Dong,Lu, Liang-Qiu,He, Gui-Feng,Bai, Jun-Chuan,Xiao, Wen-Jing
supporting information, p. 4168 - 4173 (2021/04/06)
1,3-Dienes are readily available feedstocks that are widely used in the laboratory and industry. However, the potential of converting 1,3-dienes into value-Added products, especially chiral products, has not yet been fully exploited. By synergetic photoredox/copper catalysis, we achieve the first visible-light-induced, enantioselective carbocyanation of 1,3-dienes by using carboxylic acid derivatives and trimethylsilyl cyanide. Under mild and neutral conditions, a diverse range of chiral allyl cyanides are produced in generally good efficiency and with high enantioselectivity from bench-stable and user-safe chemicals. Moreover, preliminary results also confirm that this success can be expanded to 1,3-enynes and the four-component carbonylative carbocyanation of 1,3-dienes and 1,3-enynes.
H-*BEA Zeolite-Catalyzed Nucleophilic Substitution in Allyl Alcohols Using Sulfonamides, Amides, and Anilines
Aoki, Shunsuke,Fujii, Takeshi,Morita, Sachiko,Nishida, Ryo,Ohtsuki, Akimichi,Okumura, Kazu
, (2020/07/24)
Herein, we report a novel zeolite-catalyzed nucleophilic substitution in allyl alcohols. The product yield was improved upon the addition of NaOTf (0.05 mol-percent) using the studied zeolites. The highest yields were observed using H-*BEA(Si/Al2 = 40)/NaOTf. The scope of the reaction with respect to the nucleophile was examined using 1,3-diphenylprop-2-ene-1-ol as a model substrate under optimized reaction conditions. p-Substituted aryl sulfonamides bearing electron-rich or electron-deficient substituents, alkyl sulfonamides, and heteroaryl sulfonamides undergo the amidation reaction to produce their corresponding allyl sulfonamides in good yield. Amides and anilines exhibited low activity under the optimized conditions, however, performing the reaction at 90 °C produced the target product. The scope of the allyl alcohol was investigated using p-toluenesulfonamide as the nucleophile and the reaction proceeded with a variety of allylic alcohols. To probe the practical utility of the H-*BEA-catalyzed amidation reaction, a gram-scale reaction was performed using 1.01 g (4.8 mmol) of allyl alcohol, which afforded the target product in 88 percent yield.
Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
, p. 21176 - 21182 (2020/09/17)
Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
Synthesis of a Bolm's 2,2′-Bipyridine Ligand Analogue and Its Applications
Bedná?ová, Eva,Dra?ínsky, Martin,Malatinec, ?tefan,Císa?ová, Ivana,Lamaty, Frédéric,Kotora, Martin
supporting information, p. 2869 - 2878 (2018/08/17)
A new method of synthesis of an analogue of Bolm's 2,2′-bipyridine ligand based on the catalytic [2+2+2] cyclotrimerization of 1-halodiynes with nitriles was developed. Crucial step of the whole synthesis turned out to be homodimerization of a substituted 2-bromopyridine to the corresponding bipyridine, that was studied and optimized. The newly prepared bipyridine (S,S)-2 was then tested as a chiral ligand in metal-catalyzed enantioselective reactions. Out of the studied reactions the most promising results were obtained in epoxide ring opening (82% yield, 98% ee) and Mukaiyama aldol reaction (>96% yield, 99/1 dr, 92% ee). In the case of Mukaiyama-aldol reaction as well as in the Michael addition, novel ligand 2 proved its robustness compared to Bolm's ligand as it was less sensitive to the purity of used reagents. (Figure presented.).
Copper-Catalyzed Enantioselective Conjugate Addition to α,β-Unsaturated Aldehydes with Various Organometallic Reagents
Goncalves-Contal, Sylvie,Gremaud, Ludovic,Palais, La?titia,Babel, Lucille,Alexakis, Alexandre
, p. 3301 - 3308 (2016/09/12)
β-Substituted aldehydes constitute a very important class of compounds found in nature. Synthesis of this motif can be envisioned by C-C bond formation on enals. For this purpose, we report herein the development of enantioselective copper-catalyzed conjugate addition of various organometallic reagents to α,β-unsaturated aldehydes with (R)-H8BINAP, (R)-TolBINAP, and (R)-SEGPHOS as chiral ligands. Three sets of conditions were successfully developed and several enals were used. Reactivity and regio- and enantioselectivities were strongly dependent on reaction conditions and substrates. Good to excellent regio- and enantioselectivities were obtained with zinc reagents R2Zn and aluminum reagents R3Al. However, the asymmetric conjugate addition of Grignard reagents afforded only moderate to good regio- and enantioselectivities.
A monolith immobilised iridium Cp catalyst for hydrogen transfer reactions under flow conditions
Rojo, Maria Victoria,Guetzoyan, Lucie,Baxendale, Ian. R.
, p. 1768 - 1777 (2015/02/19)
An immobilised iridium hydrogen transfer catalyst has been developed for use in flow based processing by incorporation of a ligand into a porous polymeric monolithic flow reactor. The monolithic construct has been used for several redox reductions demonstrating excellent recyclability, good turnover numbers and high chemical stability giving negligible metal leaching over extended periods of use.
Structural study-guided development of versatile phase-transfer catalysts for asymmetric conjugate additions of cyanide
Provencher, Brian A.,Bartelson, Keith J.,Liu, Yan,Foxman, Bruce M.,Deng, Li
supporting information; experimental part, p. 10565 - 10569 (2011/12/05)
Unprecedented phase-transfer catalysts for the first example of an organocatalytic asymmetric conjugate addition of cyanide with acetone cyanohydrin are reported (see scheme). Utilizing an accessible cupreidinium salt and a cyanation reagent suitable for industrial scale, this reaction holds significant promise for practical asymmetric synthesis. The catalysts were developed as a result of key structural insights gained by X-ray analysis. Copyright
Copper-catalyzed enantioselective 1,4-addition to α,β- unsaturated aldehydes
Palais, Laetitia,Babel, Lucille,Quintard, Adrien,Belot, Sebastien,Alexakis, Alexandre
supporting information; experimental part, p. 1988 - 1991 (2010/07/10)
Figure presented The first asymmetric Cu-catalyzed conjugate addition of dialkylzinc zinc reagents to a large scope of enals in presence of phosphoramidite, SimplePhos, or (R)-BINAP ligands with enantiomeric excesses up to 90% is reported. Moreover, ACA of Grignard reagents afforded moderate to good 1,4-regioselectivities with enantioselectivities up to 90%.
Boronic acid catalyzed Friedel-Crafts reactions of allylic alcohols with electron-rich arenes and heteroarenes
McCubbin, J. Adam,Hosseini, Hamidreza,Krokhin, Oleg V.
supporting information; experimental part, p. 959 - 962 (2010/04/30)
(Chemical Equation Presented) Pentafluorophenylboronic acid catalyzes the regioselective coupling of structurally diverse allylic alcohols with a variety of electron-rich aromatic and heteroaromatic substrates under ambient conditions. The commercially av
Intramolecular O-H...O hydrogen-bond-mediated reversal in the partitioning of conformationally restricted triplet 1,4-biradicals and amplification of diastereodifferentiation in their lifetimes
Moorthy, Jarugu Narasimha,Samanta, Subhas,Koner, Apurba L.,Saha, Satyajit,Nau, Werner M.
supporting information; experimental part, p. 13608 - 13617 (2009/02/06)
The photoreactivity and nanosecond transient phenomena have been investigated for a rationally designed set of ketones 4-9 in order to gain comprehensive insights concerning the influence of intramolecular hydrogen bonding on (i) the lifetimes of triplet 1,4-biradicals and (ii) the partitioning of the latter between cyclization and elimination. Comparisons of the photochemical results and lifetime data for the biradicals of ketones 6 versus 8 and 7 versus 9 revealed a remarkable influence of hydrogen bonding when superimposed upon steric factors: while 6 and 7 yielded cyclobutanols in poor yields, cyclization was found to be overwhelmingly predominant for 8-anti and moderately so for 9-anti, with a high stereoselectivity in the formation of cyclobutanols (>95% for 8-anti). The diastereochemistry in the case of 8 permitted the occurrence of fragmentation or cyclization almost exclusively (>90% cyclization for 8-anti and >75% elimination for 8-syn). Significantly, the intramolecular hydrogen bonding in the biradicals of 8 and 9 was found to reverse their partitioning between cyclization and elimination compared with the behavior of the biradicals of ketones 3; the ketones 8-anti and 9-anti underwent cyclization in benzene, predominantly leading to cyclobutanols with syn stereochemistry between the C2 and C3 substituents. In accordance with photoproduct profiles, an unprecedented ～2-fold difference in the lifetimes of the intermediate diastereomeric triplet biradicals of ketones 8 in nonpolar solvents (e.g., τsyn = 123 ns and τanti = 235 ns in cyclohexane) was observed via nanosecond laser flash photolysis, while no such difference in lifetimes was found for the triplet biradicals of acetoxy ketones 9. The intriguing diastereodifferentiation in the lifetimes of the diastereomeric triplet 1,4-biradicals of 8 and the product profiles of ketones 6, 7, and 9 are best reconciled via a unified mechanistic picture in which superposition of steric factors over varying magnitudes of O-H...O hydrogen bonding selectively facilitates a particular pathway. In particular, the diastereodifferentiation in the photochemical outcomes for the diastereomers of ketone 8 and in the lifetimes of their triplet biradicals can be understood on the basis of rapid deactivation of the 8-syn triplet biradical via fragmentation and slow cyclization of the 8-anti triplet biradical from chair- and twist-boat-like hydrogen-bonded conformations, respectively. The photolysis in polar aprotic solvents such as DMSO and pyridine was found to reverse the chemoselectivity, yielding reactivity paralleling that of ketones 3, for which the steric factors between the C2 and C3 substituents control the photochemical outcome.
