103-28-6Relevant academic research and scientific papers
Hafnium inspired activation of highly hindered anhydrides in the acylation of alcohols and polyols
Mensah, Enoch,Day, Aaron,Thomas, Raven
, p. 1094 - 1098 (2018)
A novel and highly efficient method for activating highly hindered acid anhydrides towards the acylation of alcohols and carbohydrate-derived polyols has been developed. This new method relies on the capacity of the hafnium triflate catalyst Hf(OTf)2 to activate highly hindered acid anhydrides, and to direct the acylation reaction. This new acylation protocol is mild and proceed at room temperature with low catalyst loading. The method is versatile and has been extended to different alcohol substrates with different steric encumbrance as well as carbohydrate-derived polyols to afford the corresponding ester products in good to excellent yields.
Mixed Imidazolin-2-iminato-Cp? Thorium(IV) Complexes: Synthesis and Reactivity Toward Oxygen-Containing Substrates
Karmel, Isabell S. R.,Fridman, Natalia,Tamm, Matthias,Eisen, Moris S.
, p. 2933 - 2942 (2015)
The mixed pentamethylcyclopentadienyl thorium(IV) imidazolin-2-iminato complexes Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) were synthesized in quantitative yields via rapid protonolysis of Cp?2Th(Me)2 (1) with the respective neutral imidazolin-2-iminato ligand ImRNH. Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) display short Th-N bond lengths and large Th-N-C angles. The reactivity of complex 2 and 3 toward oxygen-containing substrates was studied, and the catalytic activity of 2 was compared to the dimethyl (bispentamethyl-cyclopentadienyl) thorium complex 1. Complex 2 was applied in the catalytic Tishchenko reaction with aromatic, heteroaromatic, and branched aliphatic aldehydes, displaying a higher catalytic activity than Cp?2Th(Me)2 and Cp?2Th(ImMesN)(Me). Furthermore, 2 was applied as a catalyst in the crossed Tishchenko reaction and in the oligomerization of bis(aldehydes), as well as in the ring-opening polymerization of ε-caprolactone. In all reactions, the activity of Cp?2Th(ImDippN)(Me) (2) and Cp?2Th(ImMesN)(Me) (3) was higher than that observed for Cp?2Th(Me)2 (1), which can be attributed to the increased electron density introduced by the coordination of the imidazolin-2-iminato ligand. (Chemical Equation Presented).
Thorium complexes possessing expanded ring N-heterocyclic iminato ligands: Synthesis and applications
Ghatak, Tapas,Drucker, Shani,Fridman, Natalia,Eisen, Moris S.
, p. 12005 - 12009 (2017)
Six and seven membered N-heterocyclic iminato ligands (L) are introduced allowing access a new class of Th(iv) complexes of the type Cp?2Th(L)(CH3). These complexes were studied in the Tishchenko reaction. Stoichiometric reactions together with kinetic and thermodynamic studies permit us to propose a plausible mechanism.
Pd/C-catalyzed chemoselective hydrogenation in the presence of diphenylsulfide
Mori, Akinori,Miyakawa, Yumi,Ohashi, Eri,Haga, Tomoko,Maegawa, Tomohiro,Sajiki, Hironao
, p. 3279 - 3281 (2006)
A Pd/C-catalyzed chemoselective hydrogenation using diphenylsulfide as a catalyst poison has been developed. This methodology selectively hydrogenates olefin and acetylene functionalities without hydrogenolysis of aromatic carbonyls and halogens, benzyl esters, and N-Cbz protective groups.
Development of a practical and scalable preparation using sonication of Pd/fibroin catalyst for chemoselective hydrogenation
Kitamura, Yoshiaki,Tanaka, Asami,Sato, Mutsumi,Oono, Keiji,Ikawa, Takashi,Maegawa, Tomohiro,Monguchi, Yasunari,Sajiki, Hironao
, p. 4381 - 4388 (2007)
A practical and efficient preparation method of palladium-fibroin (Pd/Fib), silk-fibroin-supported Pd(0) by means of sonication, has been developed. The Pd/Fib catalyst could be prepared within 12 h at room temperature starting from commercial silk-fibroin and Pd(OAc)2 in MeOH, whereas our previous preparation method required at least 4 days. The present improved process is applicable to a large-scale preparation of Pd/Fib. The Pd/Fib prepared by the present method also catalyzed chemoselective hydrogenation of acetylenes, olefins, and azides in the presence of aromatic ketones, aldehydes, and halides; N-Cbz protective groups; and benzyl esters, which are readily hydrogenated under the Pd/C- or Pd/C(en)-catalyzed hydrogenation conditions. Copyright Taylor & Francis Group, LLC.
Novel palladium-on-carbon/diphenyl sulfide complex for chemoselective hydrogenation: Preparation, characterization, and application
Mori, Akinori,Mizusaki, Tomoteru,Kawase, Masami,Maegawa, Tomohiro,Monguchi, Yasunari,Takao, Shinobu,Takagi, Yukio,Sajikia, Hironao
, p. 406 - 410 (2008)
A diphenyl sulfide immobilized on palladium-on-carbon system, Pd/C[Ph 2S], was developed to achieve the highly chemoselective hydrogenation of alkenes, acetylenes, azides, and nitro groups in the presence of aromatic ketones, halides, benzyl esters, and N-Cbz protective groups. Instrumental analyses of the heterogeneous catalyst demonstrated that diphenylsul fide was embedded on Pd/C via coordination of its sulfur atom to palladium metal or physical interaction with graphite layers of the activated carbon. The catalyst could be recovered and reused at least five times without any significant loss of the reactivity.
Steric effects in the uncatalyzed and DMAP-catalyzed acylation of alcohols - Quantifying the window of opportunity in kinetic resolution experiments
Fischer, Christian B.,Xu, Shangjie,Zipse, Hendrik
, p. 5779 - 5784 (2006)
The kinetics of the reaction of several alcohols (benzyl alcohol, ethanol, 1-phenylethanol, cyclohexanol, and 1-methyl-1-phenylethanol) with a selection of anhydrides (acetic anyhydride, propionic anhydride, isobutyric anhydride, isovaleric anhydride, and pivalic anhydride) as catalyzed by 4-(N,N-dimethylamino)pyridine (DMAP)/triethyl amine have been studied in CH 2Cl2 at 20°C. In all cases the reaction kinetics can be described by rate laws containing a DMAP-catalyzed term and an uncatalyzed (back-ground) term. The rate constants for the background reaction respond sensi tively to changes in the steric demand of the alcohol and the anhydride substrates, making the reaction of cyclohexanol with acetic anhydride 526 times faster than the reaction with pivalic anhydride. Steric effects are even larger for the catalyzed reaction and the reactivity difference between acetic and pivalic anhydride exceeds a factor of 8000 for the reaction of cyclohexa nol. There is, however, no linear correlation between the steric effects on the catalyzed and the uncatalyzed part. As a consequence there are substrate combinations with dominating catalytic terms (such as the reaction of benzyl alcohol with isobutyric anhydride), while other substrate combinations (such as the reaction of cyclohexanol with pivalic anhydride) are characterized through a dominating background process. The implications of these findings for the kinetic resolution of alcohols are discussed.
Novel Template Effects of Distannoxane Catalysts in Highly Efficient Transesterification and Esterification
Otera, Junzo,Dan-oh, Nobushisa,Nozaki, Hitosi
, p. 5307 - 5311 (1991)
The transesterification of carboxylic esters and the esterification of carboxylic acids are effected under mild conditions under catalysis by 1,3-disubstituted tetraalkyldistannoxanes 1.Various functional groups remain unaffected and otherwise difficult to obtain esters are accessible.An ester bearing a tertiary butyl group in the carboxylic acid moiety remained unchanged in competition experiments with a less bulky ester, which undergoes transesterification quantitatively.The unique features of the reactions are attributable to the template effects of the dimeric structure of 1.The facility with which compounds 1 can be converted into alkoxystannoxanes 2 and the synergistic effect of the proximate tin atoms of 2 play key roles in permitting smooth reactions and high selectivity.Another notable feature of compounds 1 is their unusually high solubility in organic solvents, even though the compounds have a metaloxane core as a major skeletal part.The double-layered structure of 1, in which the inorganic moiety is surrounded by eight alkyl groups, permits esterification to be driven to completion simply by heating a mixture of the carboxylic acid and the alcohol.The distannoxane-catalyzed esterification is irreversible, and thus, no hydrolysis of the product esters occurs when compounds 1 are used as catalysts.
Reductive esterification of aromatic aldehydes using Zn/Ac 2O/imidazole or Zn/Yb(OTf)3/(RCO)2O system
Hirao, Toshikazu,Santhitikul, Sirida,Takeuchi, Hiroki,Ogawa, Akiya,Sakurai, Hidehiro
, p. 10147 - 10152 (2003)
Benzaldehydes are reduced by metallic zinc in the presence of Ac 2O and imidazole, giving the corresponding benzyl acetates in good yields. Reductive esterification of aromatic aldehydes is also carried out via gem-diacetoxy compounds. Carbonyl compounds are readily converted to the gem-diacyloxy compounds in excellent yields on treatment with 2molar amounts of acid anhydride and 10mol% of Yb(OTf)3 in MeCN at room temperature. Thus-formed diacyloxy compounds derived from aromatic aldehydes are reduced in situ by metallic zinc to afford the corresponding esters.
Sol-gel derived LaFeO3/SiO2 nanocomposite: Synthesis, characterization and its application as a new, green and recoverable heterogeneous catalyst for the efficient acetylation of amines, alcohols and phenols
Farhadi, Saeed,Jahanara, Kosar,Sepahdar, Asma
, p. 1103 - 1112 (2014)
LaFeO3/SiO2 nanocomposite was synthesized by the sol-gel process from metal nitrates and tetraethyl orthosilicate (TEOS) as the SiO2 source. The nanocomposite product was characterized by XRD, FT-IR, SEM, and surface area measurements and was used as a heterogeneous catalyst for the efficient acetylation of amines, alcohols and phenols to the corresponding acetates using acetic anhydride under solvent-free conditions. Among the various substrates, acetylation of amines was preceded rapidly, so that an amine group could be selectively acetylated in the presence of alcoholic or phenolic hydroxyl groups by the appropriate choice of reaction time. The catalyst can also be reused several times without the loss of activity. In addition, the catalytic activity of the LaFeO3/SiO2 nanocomposite was higher than that of the pure LaFeO3 nanoparticles. The method is high yielding, clean, cost effective, compatible with the substrates having other functional groups and very suitable for the practical organic synthesis.
