23522-67-0Relevant academic research and scientific papers
C-C Bond Cleavage of Unactivated 2-Acylimidazoles
Xin, Hai-Long,Pang, Bo,Choi, Jeesoo,Akkad, Walaa,Morimoto, Hiroyuki,Ohshima, Takashi
, p. 11592 - 11606 (2020/10/23)
2-Acylimidazoles are widely used as post-Transformable carboxylic acid equivalents in chemoselective and enantioselective reactions. Their transformations, however, require pretreatment with highly reactive, toxic methylating reagents to facilitate C-C bond cleavage. Here, we demonstrate that such pretreatment can be avoided and the C-C bond cleaved under neutral conditions without the use of additional reagents or catalysts. The scope of the reaction, including the use of products reported in the literature as substrates, and some mechanistic insights are described.
Asymmetric Kulinkovich Hydroxycyclopropanation of Alkenes Mediated by Titanium(IV) TADDOLate Complexes
Iskryk, Marharyta,Barysevich, Maryia,O?eka, Maksim,Adamson, Jasper,Kananovich, Dzmitry
supporting information, p. 1935 - 1948 (2019/04/26)
Asymmetric Kulinkovich cyclopropanation of carboxylic esters with prochiral alkenes is reported. The process is mediated by titanium(IV) (4 R,5 R)-TADDOLate complexes and affords correspondingly (Z)- or (E)-cyclopropanols with up to 84-87% ee in the event of intra- or intermolecular olefin ligand exchange in intermediate titanacyclopropane [titanium(II)-alkene] species. Configuration of the olefin double bond is preserved in the cyclopropane products, pointing out on total retention of configuration at Ti-C bond in the cyclopropane forming step. The results have been interpreted in the framework of ate complex mechanism, suggesting formation of pentacoordinated titanium ate species as a prerequisite of high enantiocontrol.
μ-Oxo-Dinuclear-Iron(III)-Catalyzed O-Selective Acylation of Aliphatic and Aromatic Amino Alcohols and Transesterification of Tertiary Alcohols
Horikawa, Rikiya,Fujimoto, Chika,Yazaki, Ryo,Ohshima, Takashi
supporting information, p. 12278 - 12281 (2016/08/24)
A highly chemoselective and reactive μ-oxo-dinuclear iron(III) salen catalyst for transesterification was developed. The developed iron complex catalyzed acylation of aliphatic amino alcohols with nearly perfect O-selectivity, even when using activated esters, for which chemoselectivity is more difficult to control. In addition, O-selective transesterification of aromatic amino alcohols was achieved for the first time. The high activity of the iron complex enabled the use of sterically congested tertiary alcohols, including unprecedented tert-butanol.
TEMPO-Catalyzed Oxidative Amidation of Alcohols via Hexafluoroisopropyl Esters
Vatèle, Jean-Michel
supporting information, p. 2280 - 2284 (2015/09/28)
Stepwise oxidative amidation of alcohols using trichloroisocyanuric acid, a catalytic amount of TEMPO in combination with pyridine and hexafluoroisopropyl (HFIP) alcohol followed by amines is described. This procedure used HFIP esters as activating esters which were found to be very efficient acylating agents for amide bond formation. This process is compatible with a number of functional groups and acid-sensitive protecting groups.
Oxidative esterification of aldehydes using a recyclable oxoammonium salt
Kelly, Christopher B.,Mercadante, Michael A.,Wiles, Rebecca J.,Leadbeater, Nicholas E.
, p. 2222 - 2225 (2013/06/05)
A simple, high yielding, rapid route for the oxidative esterification of a wide range aldehydes to hexafluoroisopropyl (HFIP) esters using the oxoammonium salt 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1a) is reported. These esters can be readily transformed into a variety of other functional groups. The spent oxidant (1b) can be recovered and conveniently reoxidized to regenerate the oxoammonium salt, 1a.
An efficient method for the preparation of carboxamides by dehydration condensation using tetrakis(1,1,1,3,3,3-hexafluoro-2-propoxy)silane
Tozawa, Takashi,Yamane, Yoshinobu,Mukaiyama, Teruaki
, p. 1586 - 1587 (2007/10/03)
The use of tetraalkoxysilanes, particularly tetrakis(perfluoroalkoxy) silanes, in dehydration condensation of carboxylic acids with amines was investigated. Tetrakis(1,1,1,3,3,3-hexafluoro-2-propoxy)silane, Si[OCH(CF 3)2]4, prepared easily from silicon tetrachloride and sodium 1,1,1,3,3,3-hexafluoro-2-propoxide, was found to be an effective dehydrating reagent for preparing various carboxamides in good to high yields from the corresponding carboxylic acids and amines. Copyright
