105581-83-7Relevant articles and documents
Microstructure analysis of a CO2 copolymer from styrene oxide at the diad level
Wu, Guang-Peng,Zu, Yu-Ping,Xu, Peng-Xiang,Ren, Wei-Min,Lu, Xiao-Bing
, p. 1854 - 1862 (2013/09/02)
A large amount of interesting information on the alternating copolymerization of CO2 with terminal epoxides has already been reported, such as the regiochemistry of epoxide ring-opening and the stereochemistry of the carbonate unit sequence in the polymer chain. Moreover, the microstructures of CO2 copolymers from propylene oxide and cyclohexene oxide have also been well-studied. However, the microstructure of the CO2 copolymer from styrene oxide (SO), an epoxide that contains an electron-withdrawing group, has not yet been investigated. Herein, we focus on the spectroscopic assignment of the CO2 copolymer from styrene oxide at the diad level by using three kinds of model dimer compounds, that is, T-T, H-T, and H-H. By comparing the signals in the carbonyl region, we concluded that the signals at δ=154.3, 153.8, and 153.3 ppm in the 13C NMR spectrum of poly(styrene carbonate) were due to tail-to-tail, head-to-tail, and head-to-head carbonate linkages, respectively. Moreover, various isotactic and syndiotactic model compounds based on T-T, H-T, and H-H (dimers (R,R)-T-T, (S,S)-T-T, and (R,S)-T-T; (R,R)-H-T, (S,S)-H-T, and (R,S)-H-T; (R,R)-H-H, (S,S)-H-H, and (R,S)-H-H) were synthesized for the further spectroscopic assignment of stereospecific poly(styrene carbonate)s. We found that the carbonate carbon signals were sensitive towards the stereocenters on adjacent styrene oxide ring-opening units. These discoveries were found to be well-matched to the microstructures of the stereoregular poly(styrene carbonate)s that were prepared by using a multichiral CoIII-based catalyst system. T-T races: The spectroscopic assignment of regio- and stereoregular poly(styrene carbonate)s at the diad level was performed by 13C NMR studies of three kinds of model compounds, as well as their syndiotactic (R,S) and isotactic (R,R or S,S) dimers. Copyright
A Valine-Derived Lithiated 3-Methylthiomethyl-1,3-oxazolidin-2-one for Enantioselective Nucleophilic Hydroxymethylation, Formylation, and Alkoxycarbonylation of Aldehydes
Gaul, Christoph,Seebach, Dieter
, p. 1501 - 1504 (2007/10/03)
(Equation Presented) The 3-methylthiomethyl-4-isopropyl-5,5-diphenyl-1,3-oxazolidin-2-one (I, prepared in three steps from Boc-valine ester) is lithiated and added to aldehydes, with protecting in situ trapping of the primary adducts, to give the N,S-acet
Asymmetric Synthesis of (5R,6S)-6-Acetoxy-5-hexadecanolide, the Major Component of the Oviposition Attractant Pheromone of the Mosquito Culex pipens fatigans, and Two of Its Stereoisomers
Ko, Kwang-Youn,Eliel, Ernest L.
, p. 5353 - 5362 (2007/10/02)
The benzyl derivatives of (R)- and (S)-2-hydroxydodecanal have been prepared by a previously described asymmetric synthesis based on a chiral 1,3-oxathiane and have been converted into (5R,6S)-6-acetoxy-5-hexadecanolide, a mosquito oviposition attractant pheromone, and its 5R,6R and 5S,6R stereoisomers in highly diastereoselective fashion.The steps involved are Grignard addition of 5-pentenylmagnesium bromide, Mitsunobu inversion for one of the erythro (5R,6S) isomers and oxidation-hydride reduction for the other, ozonization, oxidation, lactone formation, debenzylation, and acetylation, the overall yield in these steps being 30-42percent.
