2978-10-1Relevant articles and documents
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.
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.
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).
