2978-10-1Relevant academic research and scientific papers
Highly Active Dinuclear Titanium(IV) Complexes for the Catalytic Formation of a Carbon-Heteroatom Bond
Bhattacharjee, Jayeeta,Harinath, Adimulam,Banerjee, Indrani,Nayek, Hari Pada,Panda, Tarun K.
supporting information, p. 12610 - 12623 (2018/10/09)
A series of mononuclear titanium(IV) complexes with the general composition κ3-[R{NHPh2P(X)}2Ti(NMe2)2] [R = C6H4, X = Se (3b); R = trans-C6H10, X = S (4a), Se (4b)] and [{κ2-N(PPh2Se)2}2Ti(NMe2)2] (6b) and two dinuclear titanium(IV) complexes, [C6H4{(NPh2PS)(N)}Ti(NMe2)]2 (3c) and [{κ2-N(PPh2Se)}Ti(NMe2)2]2 (6c), are reported. Dinuclear titanium(IV) complex 6c acts as an efficient catalyst for the chemoselective addition of an E-H bond (E = N, O, S, P, C) to heterocumulenes under mild conditions. The catalytic addition of aliphatic and aromatic amines, alcohol, thiol, phosphine oxide, and acetylene to the carbodiimides afforded the corresponding hydroelemented products in high yield at mild conditions with a broader substrate scope. The catalytic efficiency of the dinuclear complex depends on the cooperative effect of the TiIV ions, the systematic variation of the intermetallic distance, and the ligand's steric properties of the complex, which enhances the reaction rate. Most interestingly, this is the first example of catalytic insertion of various E-H bonds into the carbodiimides using a single-site catalyst because only the titanium-mediated insertion of E-H into a C-N unsaturated bond is reported to date. The amine and alcohol insertion reaction with the carbodiimides showed first-order kinetics with respect to the titanium(IV) catalyst as well as substrates. A most plausible mechanism for hydroelementation reaction is also proposed, based on the spectroscopic data of the controlled reaction, a time-course study, and the Hammett plot.
Synthetic method for isourea catalyzed by rare-earth compound
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Paragraph 0038; 0039; 0046; 0047; 0056-0079, (2018/03/24)
The invention relates to a synthetic method for isourea catalyzed by a rare-earth compound. The synthetic method comprises the following steps: (1) enabling carbodiimide which is as shown in a formula (1) and alcohol which is as shown in a formula (2) to react at 25 to 60 DEG C under the catalytic action of rare earth amine to obtain the isourea, wherein the structural formulae of the formula (1) and the formula (2) are as shown in the description, wherein R1 and R2 are independently selected from C3-C8 alkyls or aryls; R3 is C1-C3 alkyls or substituted benzyls, wherein the substituted benzyls are the benzyls which contain a methyl, a naphthyl, a halogen or a pyridine ring; the rare earth amine is one of lanthanum tris[N,N-bis(trimethylsilane)amide], neodymium tris[N,N-bis(trimethylsilane)amide], samarium tris[N,N-bis(trimethylsilane)amide] or ytterbium tris[N,N-bis(trimethylsilane)amide]. According to the method, raw materials are easily obtained; the operation is simple and convenient; conditions of an application method are mild; the yield is high; the substrate application range is wide.
A novel synthesis of 2-alkylthiobenzothiazoles and 2-alkylthiobenzoxazoles
Yu, Yanfei,Li, Zhengning,Jiang, Lan
experimental part, p. 632 - 640 (2012/06/01)
3H-Benzothiazole-2-thione and 3H-benzoxazole-2-thione were selectively S-alkylated by use of O-alkylisoureas as the alkylating reagents. The reactions could be performed under mild reaction conditions in short reaction times, and high yields were obtained using O-primary-alkylisoureas, whereas low yields were obtained with sec-and tert-alkylisoureas.
Efficient synthesis of phosphonodepsipeptides derived from norleucine
Pícha, Jan,Budě?ínsky, Milo?,Han?lová, Ivona,?anda, Miloslav,Fiedler, Pavel,Vaněk, Václav,Jirá?ek, Ji?í
experimental part, p. 6090 - 6103 (2011/03/18)
In the present work, we describe in detail an efficient solution synthesis of norleucine-derived phosphonopeptides mimicking the peptide sequences Nle-Gly(Ala) and Nle-Gly(Ala)-Val. The most efficient strategy involved use of the benzyl group. The synthesis was achieved through BOP-catalysed coupling of the monobenzyl ester of the N-Cbz-protected phosphonate derivative of norleucine with the hydroxyl moieties of derivatised l-lactic or glycolic acid. Subsequently, complete deprotection of the products was achieved in good yields by one-step Pd-catalysed hydrogenolysis. We also prepared the Fmoc-Nle-Ψ[PO(OH)O]-CH2-COOH synthon and demonstrated that this precursor is a suitable building block for the solid-phase synthesis of cysteine-containing phosphonopeptides.
A model reaction for assessing the coupling and chiral efficiency of reagents in depside bond formation
Davies, John S.,Howe, Joanne,Breton, Murielle Le
, p. 2335 - 2340 (2007/10/03)
The formation of Fmoc-L-Ala-L-Phlac-OBzl (and Fmoc-D-Ala-L-Phlac-OBzl if there is racemisation) has been monitored by HPLC analysis for a number of coupling conditions between Fmoc-L-Ala-OH and H-Phlac-OBzl.For this depside link formation it is revealed that CDI, DCC/DMAP and mixed anhydride couplings gave yields near to 50percent.Couplings via TBTU, TNTU and TSTU gave lover yields.The best yields were achieved by acid chloride (61percent) urethane-N-carboxyanhydrides (80percent) and by PyBroP coupling (82percent).
Inhibition of Human Leukocyte Elastase. 2. Inhibition by Substituted Cephalosporin Esters and Amides
Finke, Paul E.,Ashe, Bonnie M.,Knight, Wilson B.,Maycock, Alan L.,Navia, Manuel A.,et al.
, p. 2522 - 2528 (2007/10/02)
A variety of 7α-methoxycephalosporin ester and amide sulfones were prepared and tested to determine the structure-activity relations for inhibition of human leukocyte elastase (HLE), a serine protease which has been implicated in several degenerative lung
