1,1 -epoxybutane, from oxidation

Some of the complexities of coordination copolymerization of alkylene oxides are highlighted by the work of Vandenberg with 2,3-epoxybutanes (88). Using the Vandenberg Catalyst, it was shown that one could selectively polymerize cis-2,3-epoxybutane from an equal mixture of cis- and trans-isomers and obtain fairly pure cis-polymer. The cis-oxide enters the crystalline polymer fraction about 20 times faster than does the trans-oxide. In the amorphous fraction of the polymer produced, the enrichment of cis-oxide was about tenfold over that of the trans-isomer. 

Zeaxanthin (135) was synthesized from the salt (133) and the dialdehyde (134) in 1,2-epoxybutane, a reagent superior to ethylene oxide particularly for polyenedialdehydes. The same salt was also used to prepare /3-cryptoxanthin and zeinoxanthin. Phenolic carotenoids from Strep-tomyces mediolani and 1,2-dihydro- and l,2,r,2 -tetrahydro-lycopene have also been obtained by conventional olefin synthesis. 

Titanium enolates.1 This Fischer carbene converts epoxides into titanium enolates. In the case of cyclohexene oxide, the product is a titanium enolate of cyclohexanone. But the enolates formed by reaction with 1,2-epoxybutane (equation I) or 2,3-epoxy butane differ from those formed from 2-butanone (Equation II). Apparently the reaction with epoxides does not involve rearrangement to the ketone but complexation of the epoxide oxygen to the metal and transfer of hydrogen from the substrate to the methylene group. 

The monomer, commonly known as tetrahydrofuran, has the systematic name tetramethylene oxide or 1,4-epoxybutane. The polymer derived from it is as often called polytetramethylene oxide as polytetrahydrofuran. In accordance with Chemical Abstracts practice, we have chosen to use the names tetrahydrofuran (THF) and polytetrahydrofuran (PTHF). 

Ethylene oxide or 1,2-epoxybutane may also be used for the synthesis of ylides. The resulting ylide is in equilibrium with its conjugated salt (equation 15). The use of ethylene oxide offers some advantages over more conventional bases used in Wittig reactions. The application is simple since ylides and most often also phosphonium salts (from phosphine and alkyl halide) need not to be prepared separately. The reaction medium is neutral, so that base-induced side reactions fail to appear. The method is however less applicable to weakly acid phosphonium salts, since deprotonation requires high temperatures (150 C). 

House showed that both cis- and /w j-2,3-epoxybutane are isomerized by magnesium bromide in ether solution to butane-2-one. The cis-epoxide also gave butane-2-one in the presence of boron trifluoride, and the trans-epoxide gave both the ketone and isobutyraldehyde. A bromohydrin has been isolated also from the low-temperature isomerization of cyclohexene oxide. ... 

EPOXYBUTANE (106-88-7) Forms explosive mixture with air (flash point -7°F/ -22°C). Unless inhibited, violent polymerization can be caused by elevated temperatures, sunlight, acids, aluminum chlorides, bases, iron, tin, potassium, sodium, sodium hydroxide, or certain salts. Reacts violently with oxidizers, alcohols. Reacts with hydroxides, metal chlorides, oxides. Flow or agitation of substance may generate electrostatic charges due to low conductivity. Storage tanks and other equipment should be absolutely dry and free from air, acetylene, ammonia, hydrogen sulfide, rust, and other contaminants. 

More recently, Bonnini and Fabio [110] reported a synthesis of (+) PS-5 starting from 2,3-epoxybutane 285 (Scheme 44), easily available by epoxidation of the monoprotected alcohol 284 according to the Sharpless method [112]. Compound 285 was oxidized to 286 and then transformed into the epoxyamide 287, which is formally related to the epoxyamide 263 prepared from L-threonine, and then cyclized to the P-lactam 288. Transformation of 288 into the (-h) PS-5 precursor 290 was accomplished in few steps according to Scheme 44. These authors also reported the synthesis of the thienamycin precursor 5 through the... 

The ring-opening copolymerization of propylene oxide and carbon monoxide forms the polyester poly(p-hydroxybutyrate) (PHA, Equation 17.52). The physical and mechanical properties of some PHAs are similar to those of isotactic polypropylene. This polymerization was first reported by Furukawa and co-workers in 1965, and more recent studies have been reported by Osakada, Rieger, and Alper. These polymerizations have been conducted with Co2(CO)j and additives. The combination of Co2(CO)j, a 1,10-phenan-throline derivative, and benzyl bromide afforded polyester with an value of 19.4 kg/ mol and M /M of 1.41. In addition to propylene oxide, 1,2-epoxybutane was successfully copolymerized with CO to yield the corresponding poly(3-hydrox5 entanoate) with an value of 16.7 kg/mol and a M /M of 1.28. The role of benzyl bromide is unclear. Related copolymerizations of aziridines and CO to form polyamides have also been reported. Polymer values as high as 27.5 kg/mol have been reported, and tjqjical M /M values varied from 1.11 to 1.64. 

In efforts to elucidate the mechanism of the original ZnEt2/H20 catalyst system, Inoue described the synthesis of polycarbonates from several optically active epoxides including styrene oxide (SO) (8,9), 3-phenyl-1,2-epoxypropane (10), cyclohexylepoxyethane (77) and 1,2-epoxybutane (EB) (P). The properties of the polycarbonates, however, are not discussed in these accounts. Other epoxides copolymerized by Inoue using the ZnEt2/H20 catalyst system include 1,2-, and 2,3-EB and isobutylene oxide (72) and glycidol ethers and carbonates (13). 

The polymerization of 2,3-epoxybutane with the same initiator as used with propylene oxide shows that the oxygen/substituted-carbon atom bond can be cleaved and, hence, a mechanism can be logically proposed to account for the head-to-head, tail-to-tail structures identified by Price and Vandenberg. With 2,3-epoxybutane, it was found that amorphous polymer could also be as pure disyndiotactic as the crystalline forms. Amorphous polymer could arise from short sequences of stereoregularity that were too short to form crystallizable segments. These could arise when coordination of monomer temporarily displaced alkoxide, interrupting chain growth, which, when resumed, could be selective for the antipode monomer. 

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. 

If, however, a complex initiator based on aluminum or zinc alkyls is used, a product with identical chemical constitution but entirely different physical characteristics results. The reason for this is that the individual polymer chains are produced from either one or the other of the two stereoisomers. The polymer formed from the racemic mixture of d- and /-propylene oxides is a solid thermoplastic with a crystalline melting point of about +75°C. An even more dramatic result was obtained by Vandenberg with the polymerization of 2,3-epoxybutane ... 

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