Trans-2,3-Epoxybutane

Carbonylative kinetic resolution of a racemic mixture of trans-2,3-epoxybutane was also investigated by using the enantiomerically pure cobalt complex [(J ,J )-salcy]Al(thf)2 [Co(CO)4] (4) [28]. The carbonylation of the substrate at 30 °C for 4h (49% conversion) gave the corresponding cis-/3-lactone in 44% enantiomeric excess, and the relative ratio (kre ) of the rate constants for the consumption of the two enantiomers was estimated to be 3.8, whereas at 0 °C, kte = 4.1 (Scheme 6). This successful kinetic resolution reaction supports the proposed mechanism where cationic chiral Lewis acid coordinates and activates an epoxide. 

The polymerization of optically pure propylene oxide by FeCl3 -derived initiators yields an optically active polymer. E. J. Vandenberg [J. Polym. Sci., A-l(7), 525 (1969)] attempted to gain insight into the mechanism by polymerizing the 2,3-epoxybutanes. The optically active trans-2,3-epoxybutane was polymerized to an optically inactive crystalline polymer. Evaluate this result and discuss its implications on the propagation mechanism for propylene oxide polymerization. 

Nonsuperposable mirror-image (enantiomeric) forms of trans- 2,3-epoxybutane... 

Reaction of rran.s-2-butene with m-chloroperoxybenzoic acid yields trans-2,3-epoxybutane. A mixture of enantiomers is formed because the peroxyacid can attack either the top or bottom of the double bond. 

The clear cut case of enantiomorphic selection has been reported by Vander-berg ° ) in polymerization of trans-2,3-epoxybutanes ... 

The synthesis of butadiene dioxide with air at 250° has been described. The epoxidation of 2-butene takes place partly stereospecifically to trans-2,3-epoxybutane. ... 

The Hg-sensitized photolysis of several ethers in the liquid phase was briefly studied by Tsao (264). The gas phase photosensitized decomposition of ethers has found much more interest. In Steacie s group before 1950 there were investigated diethyl ether (265), ethylene oxide (266), and dimethyl ether (267). Cvetanovic and co-workers studied ethylene oxide (268) and trans-2,3-epoxybutane (269). Subsequent work on dimethyl ether was done by Pottle et al. (259), Takezaki et al. (270), Loucks and Laidler (271), and Payette et al. (252). The Hg-sensitized... 

Epoxidation. Mimoun et at3 report that the M0O5 HMPT complex reacts with olefins to form epoxides in high yield. Alkyl substituents on the double bond increase the rate of epoxidation. Aprotic solvents also enhance the rate highest rates are observed in methylene chloride. The reaction is very slow in DMF or THF. The epoxidation is stereospecific with retention of configuration of the olefin. Thus m-butene-2 is converted into cis-2,3-epoxybutane and >ra . -butene-2 into trans-2,3-epoxybutane. The French chemists proposed the mechanism shown in scheme I. 

In a recent paper we reported the results of our investigation on the peroxo-derivatives of TS-1 (hereafter referred.as TS-l-Oj) [45]. TS-I-O2 shows an acidity that is much higher than that of TS-1 or Silicalite-1 or Silicallte-1/H202 the first one in fact hydrolizes much more faster the trans-2-3-epoxybutane than the latter three. The acidity of TS-l-Oj may come from one of these two situations ... 

A Ti-O-OH unit is able to form a five membered cyclic structure with a donor hydroxyl moiety coordinated on Ti as represented in the scheme (II). The cyclic structure can produce a significant increase of both stability and acid dissociation. We observed also that the acid activity of TS-I-O2 is solvent dependent. The hydrolysis rate of trans-2-3-epoxybutane decreases in the order CH3OH > CjHgOH > H2O. This behaviour is consistent with the presence of cyclic complexes like ... 

In work investigating the mechanism of this system, Vandenberg used AIR3/H2O catalysts to polymerize cis- and trans-2,3-epoxybutane. Mechanistic information for the polymerization was obtained from the properties of the resultant polymers and the examination of the diol decomposition products. These results are summarized in Scheme 4... 

Vandenberg, following a particularly penetrating line of research, used the polymerization of cis- and trans-2,3-epoxybutane to distinguish the polymerization mechanisms of oxirane coordination polymerization and then to generalize this basic mechanism to monosubstituted oxiranes (95). The mechanism... 

At low temperatures, about -78°C, in triisobutylaluminum/ water-initiated polymerization, which is presumed to be a cationic initiation, an amorphous (elastomeric) polymer is obtained from cis-2,3-epoxybutane, and a crystalline polymer, melting point 100°C, is obtained from the trans-isomer. In a copolymerization of the two isomers, the cis-oxide enters the copolymer at about twice the rate of the trans-isomer. Further, the low-temperature, cationic poly(trans-2,3-epoxybutane) with a crystalline melting point of 100°C was found to consist of diad units with a mesodiisotactic structure, while the crystalline polymer formed by coordinate polymerization of the cis-monomer, melting point 162°C, had diad units that were racemic diisotactic. These results make apparent the importance of the monomer coordination step in polymer chain growth in coordinate polymerizations. 

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