Gang Wang,Li Peng,Yaochen Zheng,Yanqin Gao,Xuedong Wu,Tianhui Ren,Chao Gao,Jin Han
We describe a novel triethylamine catalyzed S → O acetyl migration reaction for yielding thiol compounds under mild conditions through the formation of a transitional 5-membered ring. A series of epoxy compounds have been transformed into their thiol counterparts which could be used for construction of topological and functional sulfur-containing polymers. The one-pot two-step processes including the S → O acetyl migration and the following thiol-click reactions avoided separation of thiol intermediates. Applying these processes on a new-type latent polythiols overcomes crosslinking problem usually met in preparation of multithiol compounds due to the formation of disulfide bonds.
This work investigated the reaction behaviors of diethylamine (DEA) catalytic oxidation on various Cu-based catalysts with different supports (TiO 2 , HZSM-5(27), HZSM-5(130) and S-1). It was found that the acidic environment of catalysts greatly influenced reaction pathways of DEA oxidation. On Cu 5 /TiO 2 catalyst mainly with Lewis acidity, DEA preferentially dissociated through a two-step dehydrogenation to produce acetonitrile and ethylene, while on Cu 5 /HZSM-5(27) catalyst with strong Brønsted acidity, DEA could directly decompose into ethylamine and ethylene via N-C cleavage. Both pathways existed simultaneously over Cu 5 /HZSM-5(130) with decreased Brønsted acidity. Thereafter, acetonitrile could be further oxidized on the Cu 5 /TiO 2 catalyst to generate a large amount of NO x via NCO(a) intermediates over-oxidation, while ethylamine on Cu 5 /HZSM-5 samples would convert to acetamide and then produced N 2 and CO 2 . The Cu 2+ species due to enriched Brønsted acid sites in Cu 5 /HZSM-5 catalysts ensured excellent N 2 selectivity via internal SCR mechanism. Additionally, the strong Brønsted acidity of Cu 5 /HZSM-5(27) could induce the polymerization of carbonaceous intermediates and thereby resulted in severe coke deposition. As for Cu 5 /HZSM-5(130) and Cu 5 /S-1 with relatively lower Brønsted acidity and reducibility would release some unwanted gas-phase by-products like ethyl-isocyanate. This work provided useful guidance for designing NVOCs catalysts with high activity and less toxic by-products.
An optical polythiourethane based on m-xylylene diisocyanate (XDI) and 4-mercaptomethyl-3,6-dithia-1,8-octanedithiol (BES) has been studied. Triethylamine was adopted as a catalyst, and the solid-state isothermal cure reaction was carried out using FTIR spectroscopy, in the temperature range of 75°C-105°C. The -NCO absorption band of XDI was used to monitor the conversion of diisocyanate into polythiourethane. The reaction rate enhanced with an increase in the content of the catalyst, and the gel time determined by swelling test was shorter for the system with higher catalyst content. Kinetic parameters were calculated from the infrared spectrum data, and the results showed that the curing reaction of polythiourethane accords with first-order kinetic characteristics. The activation parameters obtained from the evaluation of kinetic data were , , and . The observed negative entropy of activation value supported the formation of a transition state in the cure reaction.
24 Aza-Michael adducts were synthesised in moderate to excellent yields by the addition of 5-substituted uracils to acrylates with ethylamine as a catalyst. Many of the adducts were obtained in almost quantitive yield without column chromatography. The procedure provideded an efficient approach to the synthesis of N-1 uracil adducts using acrylates as acceptors. The structures of the compounds were determined by 1H NMR, 13C NMR, mass spectra and X-ray crystallography analyses. The uracil unit is present in DNA and related natural products and has a broad spectrum of biological activity.
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