2- Methyloxirane

Second-generation juvenoids incorporate more substantial stmctural departures from neotenin and are more resistant to metaboHc and environmental degradation. Epiphenonane, 2-ethyl-3-[3-ethyl-5-(4-ethylphenoxy)-pent-3-en-yl] 2-methyloxirane (131), has a rat oral LD q of 4000 mg/kg. It and similar juvenoids are used in China and Japan to prolong the last larval instar of the silkworm so that silk production is increased 10—15%. Fenoxycarb, ethyl [2-(4-phenoxyphenoxy)ethyl] carbamate (132) (mp 53°C, vp 0.0078 mPa at 20°C), is soluble in water to 6 mg/L. The rat oral LD q is >16,800 mg/kg. Fenoxycarb has a wide spectmm of activity, interfering with the developmental processes of fleas, cockroaches, and ants. 

Propylene oxide [75-56-9] (methyloxirane, 1,2-epoxypropane) is a significant organic chemical used primarily as a reaction intermediate for production of polyether polyols, propylene glycol, alkanolamines (qv), glycol ethers, and many other useful products (see Glycols). Propylene oxide was first prepared in 1861 by Oser and first polymerized by Levene and Walti in 1927 (1). Propylene oxide is manufactured by two basic processes the traditional chlorohydrin process (see Chlorohydrins) and the hydroperoxide process, where either / fZ-butanol (see Butyl alcohols) or styrene (qv) is a co-product. Research continues in an effort to develop a direct oxidation process to be used commercially. 

Propylene oxide 1,2-Epoxypropane 2-Methyloxirane 2-Methyloxacyclopropane Cyclohexene oxide 1,2-Epoxycyclohexane 7-Oxabicyclo[4.1.0]heptane ... 

Oxirane (1) and methyloxirane (3) are miscible with water, ethyloxirane is very soluble in water, while compounds such as cyclopentene oxide and higher oxiranes are essentially insoluble (B-73MI50501) (for a discussion of the solubilities of heterocycles, see (63PMH(l)l77)). Other physical properties of heterocycles, such as dipole moments and electrochemical properties, are discussed in various chapters of pmh. The optical activity of chiral oxiranes has been investigated by ab initio molecular orbital methods (8UA1023). 

Recently (79MI50500) Sharpless and coworkers have shown that r-butyl hydroperoxide (TBHP) epoxidations, catalyzed by molybdenum or vanadium compounds, offer advantages over peroxy acids with regard to safety, cost and, sometimes, selectivity, e.g. Scheme 73, although this is not always the case (Scheme 74). The oxidation of propene by 1-phenylethyl hydroperoxide is an important industrial route to methyloxirane (propylene oxide) (79MI5501). 

The manufacture and uses of oxiranes are reviewed in (B-80MI50500, B-80MI50501). The industrially most important oxiranes are oxirane itself (ethylene oxide), which is made by catalyzed air-oxidation of ethylene (cf. Section 5.05.4.2.2(f)), and methyloxirane (propylene oxide), which is made by /3-elimination of hydrogen chloride from propene-derived 1-chloro-2-propanol (cf. Section 5.05.4.2.1) and by epoxidation of propene with 1-phenylethyl hydroperoxide cf. Section 5.05.4.2.2(f)) (79MI50501). 

Oxirane is used as a fumigant for grain and a sterilant e.g. for space vehicles bound for putative abodes of life), but mainly for the manufacture of 1,2-ethanediol ( ethylene glycol ), emulsifiers, plastics and resins (below), plasticizers, synthetic rubber and synthetic fibers. Methyloxirane is used mainly to make detergents, hydraulic fiuids and lubricants. 

The reference compound methyloxirane gives the H NMR spectrum 11a shown with expanded multiplets. What information regarding its relative configuration can be deduced from the expanded H multiplets of monordene displayed in 11b ... 

The relative configurations of vicinal protons follow from the characteristic values of their coupling constants. Thus 16.1 Hz confirms the trans relationship of the protons on C-8 and C-9, 10.8 Hz confirms the cis relationship of the protons on C-6 and C-1. The 2.0 Hz coupling is common to the oxirane protons at = 3.00 and i.27 this value fixes the trans relationship of the protons at C-4 and C-5 following a comparison with the corresponding coupling in the methyloxirane (2.6 Hz). The anti relationship of the protons A-H and h-H can be recognised from their 8.7 Hz coup-... 

Chemical Designations - Synonyms 1,2-Epoxypropane Methyloxirane propene oxide Chemical Formula CH3CHCH2O. 

Upon carefully controlled hydrolysis with hydrochloric acid at room temperature, the corresponding serine methyl esters 4 are obtained in reasonable yields. Higher yields of 4 arc obtained by hydrolyzing with dilute trifluoroacetic acid5. In some cases, the diastereomeric ratio of 4 does not exactly correspond to the d.r. of the adduct 3, which is attributed to different kinetics in the hydrolysis of the diastereomers 4. Subsequent treatment of the methyl ester with excess 5 N hydrochloric acid and methyloxirane as an acid scavenger results in the free amino acid 54,7. 

S)-methyloxirane for different rotational positions of the methyl group. Reproduced, with permission, from Ref. [60],... 

In the case of methyloxirane, however, on Pt and Pd catalysts the extent of the rupture of the sterically hindered bond is indicative of the electrophilic character of the catalyst. Unsupported or silica-supported ion-exchanged catalysts cleave the sterically less hindered bond, whereas on the impregnated catalysts, the rupture of the more hindered C-O bond is dominant.290 It is likely that Pt or Pd surface metal ions are responsible for the rupture of the sterically more hindered bond and residual chlorine from the catalyst preparation can stabilize these ions in the hydrogen atmosphere. 

Bromomethyl)-lithium in the Preparation of Oxiranes Ethyl 2-Methyloxirane-2-propanoate. 

Lewis acid SnCLj-assisted reaction between the l,3-thiazole-5-thione 434 and /ra r-2,3-dimethyloxirane led to the m 4,5-dimethyl-l,3-oxathiolane 435 The same Lewis acid enabled a second addition of /ra/ -2,3-dimcthyloxirane onto the C—N bond of the 1,3-thiazole ting of 434, leading to the formation of the tetrahydro-2//-thiazolo[2,3- ]-oxazole adduct 436 (Equation 200) <2000HCA3163>. Condensation of 2,4-dinitroimidazole, 8-bromotheophylline, and 8-bromoadenine with substituted methyloxiranes involved sequential A -alkylation-r/wo-substitution and furnished a series of 2,3-dihydro-imidazo[2,l- ]oxazole derivatives 437, 438, and 439 (Equations 201-203) <2000CCC1126, 2000EJ03489, 2005TL3561, 2004JHC51>. 

A novel aromatic substitution reaction with electron-deficient radicals, which avoids the use of stannanes, is promoted by the addition of tetra-n-butylammonium bromide [54]. Iodoacetonitrile and iodoacetic esters react with pyrroles and indoles in good to high yield upon photolysis in the presence of 2-methyloxirane and sodium thiosulphate (Scheme 6.34). 

The iodoalkane (1 mmol) and an excess of the heteroarene (5-15 mmol), Na2S203 (0.16 g), 2-methyloxirane (0.3 g), and TBA-Br (32 mg, 0.1 mmol) are added to MeOCMe3 (2 ml) in a Pyrex tube. The mixture is degassed under Ar at 0°C and photol-ysed for 36-48 h with a medium pressure Hanovia lamp. Et20 (10 ml) is added to the mixture and the organic phase is separated, washed well with H20, dried (MgS04), and evaporated to yield the substituted heteroarene. 

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. 

Disubstituted oxiranes of general structure 10.44, namely 2-alkyl-3-methyloxiranes, are another case in point. Again, nucleophilic attack is exclusively or predominantly at the more accessible C(3), with substrate... 

---