Oxirane 2-butyl

An oxirane process utilizes ethylbenzene to make the hydroperoxide, which then is used to make propylene oxide [75-56-9]. The hydroperoxide-producing reaction is similar to the first step of cumene LPO except that it is slower (2,224,316—318). In the epoxidation step, a-phenylethyl alcohol [98-85-1] is the coproduct. It is dehydrated to styrene [100-42-5]. The reported 1992 capacity for styrene by this route was 0.59 X 10 t/yr (319). The corresponding propylene oxide capacity is ca 0.33 x 10 t/yr. The total propylene oxide capacity based on hydroperoxide oxidation of propylene [115-07-1] (coproducts are /-butyl alcohol and styrene) is 1.05 x 10 t/yr (225). 

There are other commercial processes available for the production of butylenes. However, these are site or manufacturer specific, eg, the Oxirane process for the production of propylene oxide the disproportionation of higher olefins and the oligomerisation of ethylene. Any of these processes can become an important source in the future. More recentiy, the Coastal Isobutane process began commercialisation to produce isobutylene from butanes for meeting the expected demand for methyl-/ rZ-butyl ether (40). 

Oxirane Process. In Arco s Oxirane process, tert-huty alcohol is a by-product in the production of propylene oxide from a propjiene—isobutane mixture. Polymer-grade isobutylene can be obtained by dehydration of the alcohol. / fZ-Butyl alcohol [75-65-0] competes directly with methyl-/ fZ-butyl ether as a gasoline additive, but its potential is limited by its partial miscibility with gasoline. Current surplus dehydration capacity can be utilized to produce isobutylene as more methyl-/ fZ-butyl ether is diverted as high octane blending component. 

The oxaziridine ring itself is stable towards alkali there is, for instance, no substitutive ring opening by hydroxyl ions as in oxiranes. 2-r-Butyl-3-phenyloxaziridine (56) is not attacked by methoxide ion in methanol during 12 h at room temperature 3-isopropyl-2-r-octyloxaziridine does not react at room temperature with either solid potassium hydroxide or potassium methoxide solution (57JA5739). 

Opening of the oxirane with tertiary butyl amine would then complete construction of the 3-blocking side chain (40). Displacement of chlorine by hydrazine then affords... 

A comparison of the configuration of the substrates and reaction products shows that the oxiranyl anions arc configurationally stable under the reaction conditions. Only one example is known in which isomerization was observed. When the ci.v-tm-butyl-substituted epoxysilane27 was metalated and quenched with 2-cyclohexenone, addition product 27 was obtained under inversion of the anionic center. Presumably the strain created in forcing the ter/-butyl and the trimethylsilyl group cis on the oxirane ring facilitates the isomerization process13. 

Figure 2. Conversion versus time for substitution by tetrabutyl-ammonium benzoate on poly(epibromohydrin) (O) poly[(2-bromo-ethyl )oxirane] (0) poly[(3-bromopropyl )oxirane] (v, , separate runs) and poly [(4-bromo butyl )oxirane] (a, , separate runs).

Formation of the conjugate base of phosphine under the conditions of aqueous dioxane and KOH with red phosphorus allows also for the formation of C-P bonds by attack of oxiranes.33 Under these conditions, mixtures of phosphines and phosphine oxides are formed. Using red phosphorus in liquid ammonia with sodium metal and f-butyl alcohol, good yields of primary (2-hydroxyalkyl)phos-phines are obtained.34... 

Oxirane A general process for oxidizing olefins to olefin oxides by using an organic hydroperoxide, made by autoxidation of a hydrocarbon. Two versions are commercial. The first to be developed oxidizes propylene to propylene oxide, using as the oxidant f-butyl hydroperoxide made by the atmospheric oxidation of isobutane. Molybdenum naphthenate is used as a... 

Epoxidation of ot.fl-unsaturated ketones by hydrogen peroxide or /-butyl peroxide is promoted by the addition of tetra-n-butylammonium fluoride [10], whereas the corresponding reaction with 1,4-disubstituted but-2-en-l,4-diones is catalysed by quaternary ammonium iodides [11], Oxiranes are also produced by the catalysed reaction of /-butyl peroxide with a,f)-unsaturated sulphonates under basic conditions [12]. 

Direct phase-transfer catalysed epoxidation of electron-deficient alkenes, such as chalcones, cycloalk-2-enones and benzoquinones with hydrogen peroxide or r-butyl peroxide under basic conditions (Section 10.7) has been extended by the use of quininium and quinidinium catalysts to produce optically active oxiranes [1 — 16] the alkaloid bases are less efficient than their salts as catalysts [e.g. 8]. In addition to N-benzylquininium chloride, the binaphthyl ephedrinium salt (16 in Scheme 12.5) and the bis-cinchonidinium system (Scheme 12.12) have been used [12, 17]. Generally, the more rigid quininium systems are more effective than the ephedrinium salts. 

Basic solid liquid two-phase conditions with f-butyl peroxide and N-benzylquininium chloride convert cyclohex-2-enone preferentially into the 2(S),3(S)-oxirane (20% ee) which, upon purification and treatment with hydrazine, yields (S)-cyclohex-2-enol [7]. This reaction contrasts with the direct reduction of cyclohex-2-enone to the /J-isomer by lithium aluminium hydride in the presence of quinine [20]. 

The patterns of regio- and stereoselectivities become more complex in disubstituted oxiranes. Beginning with 2,2-disubstituted oxiranes, attack is always at the accessible C-atom. In terms of substrate enantioselectivity, it was found that 2-butyl-2-methyloxirane (2-methyl-1,2-epoxyhexane, 10.43, R = Bu) was hydrolyzed with a preference for the (5)-enantiomer. This substrate enantioselectivity was lost for branched analogues, namely 2-(/er/-bu-tyl)-2-methyloxirane (10.43, R = /-Bu) and 2-(2,2-dimethylpropyl)-2-meth-yloxirane (10.43, R = (CH3)3CCH2) [124], Thus, it appears that the introduction of a geminal Me group suppresses the enantioselectivity seen with branched monoalkyloxiranes, and reverses it for straight-chain alkyloxiranes. 

Finally, a reaction that clearly shows the electrophihc carbenoid-type character of a-lithiated epoxides is the reductive alkylation discovered by CrandaU and Apparu. The transformation is illustrated by the treatment of f-butyl ethylene oxide with t-butyllithium to yield ii-di-f-butylethene (equation 55). The overall reaction results in a conversion of an oxirane into an aUcene under simultaneous substitution of an a-hydrogen atom by the alkyllithium reagent ... 

S)-leucine, and (S)-sec-butyl-(R)-oxirane from (2S,3S)-isoleucine, respectively. This useful three-step route complements the synthesis of (S)-alkyloxiranes from (S)-2-araino acids via (S)-2-hydroxy acids,with retention of configuration at the stereocenter. 

The chlorohydrins show different rates of cyciization, reflecting the steric hindrance of residue R. The most vigorous reaction is observed in the case of (S)-2-chloropropan-l-ol (R = CH3) only 30°C at 100 mm is required. For (R)-isopropyloxirane, the temperature of the bath is raised slowly to 50°C, and after 40 min to 60°C, while the pressure is reduced to 50 ram for an additional 5 min. For the higher boiling oxiranes, e.g., (R)-isobutyloxirane and (S)-sec-butyl-(R)-oxirane [(2R,3S)-3-methyl-1,2-epoxybutane] , the temperature is raised slowly to 60°C within 1 hr, while the pressure is reduced carefully to 30 mm. 

Reaction of the anion of tert-butyl isocyanoacetate with oxiranes gives the y-hydroxy products 11, which upon mesylation can be transformed by an intramolecular alkylation to the iso-cyanocyclopropanecarboxylates 12, the precursors of 1-amino-cyclopropanecarboxylates100. The cyclization 11 — 12 shows a relatively high degree of stereoselectivity due to the difference in bulkiness betwen the isocyano and the tert-butoxycarbonyl groups. 

Ein Beispiel fur eine intramolekular und stereospezifisch ablaufende N-(2-Hydroxy-alky-lierung) ist die Bildungder beiden stcreoisomcrcn 2-(I-Hydroxy-propyl)-piperidine ( ) a-Conhydrin (I 90%) bzw. ( J-fi-Conhydrin (II 88%) durch Erhitzen von trans- bzw. m-l-(4-Amino-butyl)-2-ethyl-oxiran in Toluol oder Benzol1. 

---