18335-33-6Relevant academic research and scientific papers
Investigation of the Deprotonative Generation and Borylation of Diamine-Ligated α-Lithiated Carbamates and Benzoates by in Situ IR spectroscopy
Mykura, Rory C.,Veth, Simon,Varela, Ana,Dewis, Lydia,Farndon, Joshua J.,Myers, Eddie L.,Aggarwal, Varinder K.
supporting information, p. 14677 - 14686 (2018/11/20)
Diamine-mediated α-deprotonation of O-alkyl carbamates or benzoates with alkyllithium reagents, trapping of the carbanion with organoboron compounds, and 1,2-metalate rearrangement of the resulting boronate complex are the primary steps by which organoboron compounds can be stereoselectively homologated. Although the final step can be easily monitored by 11B NMR spectroscopy, the first two steps, which are typically carried out at cryogenic temperatures, are less well understood owing to the requirement for specialized analytical techniques. Investigation of these steps by in situ IR spectroscopy has provided invaluable data for optimizing the homologation reactions of organoboron compounds. Although the deprotonation of benzoates in noncoordinating solvents is faster than that in ethereal solvents, the deprotonation of carbamates shows the opposite trend, a difference that has its origin in the propensity of carbamates to form inactive parasitic complexes with the diamine-ligated alkyllithium reagent. Borylation of bulky diamine-ligated lithiated species in toluene is extremely slow, owing to the requirement for initial complexation of the oxygen atoms of the diol ligand on boron with the lithium ion prior to boron-lithium exchange. However, ethereal solvent, or very small amounts of THF, facilitate precomplexation through initial displacement of the bulky diamines coordinated to the lithium ion. Comparison of the carbonyl stretching frequencies of boronates derived from pinacol boronic esters with those derived from trialkylboranes suggests that the displaced lithium ion is residing on the pinacol oxygen atoms and the benzoate/carbamate carbonyl group, respectively, explaining, at least in part, the faster 1,2-metalate rearrangements of boronates derived from the trialkylboranes.
Asymmetric hydrogenation of tert-alkyl ketones: DMSO effect in unification of stereoisomeric ruthenium complexes
Yamamura, Tomoya,Nakatsuka, Hiroshi,Tanaka, Shinji,Kitamura, Masato
supporting information, p. 9313 - 9315 (2013/09/12)
Face off: The ruthenium complexes of a new axially chiral PNNligand (L) are highly efficient in the presence of dimethylsulfoxide (DMSO) for hydrogenation of both functionalized and unfunctionalized tert-alkyl ketones. DMSO is thought to narrow down the many possible complex stereoisomers into a single facial L/Ru complex, thus enhancing the reactivity, selectivity, and productivity. Copyright
Highly chemoselective reduction of carbonyl groups in the presence of aldehydes
Bastug, Gulluzar,Dierick, Steve,Lebreux, Frederic,Marko, Istvan E.
supporting information; experimental part, p. 1306 - 1309 (2012/05/20)
The exquisite ability of diethylaluminum benzenethiolate to efficiently discriminate between aldehydes and other carbonyl functions enables the chemoselective in situ reduction of ketones and methyl esters in the presence of aldehydes. This potent strateg
N-heterocyclic carbene-catalyzed hydrosilylation of styryl and propargylic alcohols with dihydrosilanes
Zhao, Qiwu,Curran, Dennis P.,Malacria, Max,Fensterbank, Louis,Goddard, Jean-Philippe,Lacote, Emmanuel
supporting information; experimental part, p. 9911 - 9914 (2011/10/05)
Reducing alkenes to tears: Addition of structurally diverse N-heterocyclic carbenes (NHCs) to silicon allows the reduction of propargylic and styryl alcohols through an organocatalyzed silylation/direct hydride transfer tandem reaction (see scheme). Catalytic turnover is enabled by the switch to and from hypervalent silicon. This provides a new synthetic application of NHC-main group element complexes. Copyright
Chemoselective conjugate reduction of α,β-unsaturated ketones catalyzed by rhodium amido complexes in aqueous media
Li, Xuefeng,Li, Liangchun,Tang, Yuanfu,Zhong, Ling,Cun, Linfeng,Zhu, Jin,Liao, Jian,Deng, Jingen
supporting information; experimental part, p. 2981 - 2988 (2010/07/05)
Although a notable feature of Noyori's Ru-TsDPEN complex is that the transfer hydrogenation reaction is highly chemoselective for the C-O functional group and tolerant of alkenes, our early report indicated that the chemoselectivity could be switched from C-O to C-C bonds in the transfer hydrogenation of activated α,β-unsaturated ketones. Now we have found that a variety of α,β-unsaturated ketones, even without other electron-withdrawing functional groups, could be reduced on the alkenic double bonds with high selectivities employing amido-rhodium hydride complex in aqueous media, and up to 100% chemoselectivity has been achieved. It is notable that the chemoselectivity was improved significantly on going from organic solvent to water. Moreover, a 1,4-addition mechanism has been proposed on the basis of the corresponding experimental details and computational analysis.
[Ru(DMSO)4] Cl2 catalyzes the α-alkylation of ketones by alcohols
Martínez, Ricardo,Brand, Gabriel J.,Ramón, Diego J.,Yus, Miguel
, p. 3683 - 3686 (2007/10/03)
The electrophilic α-alkylation of ketones with alcohols was accomplished by a [Ru(DMSO)4]Cl2 catalyzed process, water being the only wasted material. The reaction can be successfully governed to produce either the expected ketones or their related alcohols only by changing the reaction conditions. When 2-aminobenzyl alcohol was used, a cyclization process took place to yield 2,3-disubstituted quinolines.
