3-Methylene oxirane

The high CH stretching frequencies of three-membered rings of this type reflects their well-known hmsaturated character , and for the same reason they are sometimes difficult to differentiate from aromatic or olefinic absorptions. Absorption above 3000 cm can also arise in special cases in four-membered rings which contain polar groups able to influence the hybridisation of the CH bonds. 3-butyrolactone [121] is such a case with CH bands at 3014 and 2933 cm Other examples are 3-methylene oxirane [122] and cyclobutanone [123]. 

Many other reagents for converting alkenes to epoxides,including H2O2 and Oxone , VO(0-isopropyl)3 in liquid C02, ° polymer-supported cobalt (II) acetate and 02, ° and dimethyl dioxirane.This reagent is rather versatile, and converts methylene oxiranes to spiro-epoxides. ° ° One problem with dimethyloxirane is C—H insertion reactions rather than epoxidation. Magnesium monoperoxyphthalate is commercially available, and has been shown to be a good substitute for m-chloroperoxybenzoic acid in a number of reactions. 

Although steroidal spiro oxiranes are difficult to obtain stereochemically pure by peracid epoxidations of exocyclic methylenes,the recently developed methylene transfer reagents, dimethylsulfonium methylide and di-methylsulfoxonium methylide in tetrahydrofuran, proved useful in the stereoselective transformation of steroid ketones to a- and -oxiranes, (87) and (88), respectively. ... 

In nuclear magnetic resonance (NMR) spectra the protons of the oxirane ring are usually shifted out of the steroid methylene envelope. Tori et al have tabulated the relationships of the angular methyl proton resonances and the oxirane proton signals with respect to location and configuration of the oxirane group. 

A solution of 17-cyanoandrosta-5,16-dien-3jS-ol acetate (46 g) and anhydrous potassium acetate (0.46 g) in methylene dichloride (310 ml) is treated with a mixture of 40% peracetic acid (37 ml) and anhydrous potassium acetate (1.84 g) in methylene dichloride (46 ml), the temperature of the solution being maintained below 25°. The mixture is stored at room temperature for 4 hr and then washed successively with water, 5% sodium bicarbonate solution (aqueous sodium bisulfite, 10g/150g water, has been used to decompose excess reagent before workup) and water until neutral. Evaporation of the dried solution and addition of ether gives 24.1 g of 5oc,6a-epoxy-17-cyanoandrost-16-en-3 -ol acetate mp 187-190°. One recrystallization from methanol gives 20.4 g of oxirane melting at 191-194°. 

The methylene protons that are very close to the oxirane oxygen atom are deshielded and appear as a broader signal near 8 = 4.2. This deshielding appears to be due to both van der Waals interactions between protons and the oxygen atom 331 and the effect of the unshared electron pair at the heteroatom 34). 

The l-oxa-2,4,5-cycloheptatrienes 602 and 603 were postulated to be intermediates in the rearrangement of certain (ethynylfuryl)oxiranes to furo[3,4-b]furans [251]. The replacement of the methylene groups of 1,2-cycloheptadiene (465) by SiMe2 groups and the introduction of substituents at the allene moiety allowed the preparation of isolable seven-membered ring allenes. Thus, Barton et ah [177] obtained 604 and Ando et al. [178] 605. A few reactions of these systems have also been studied [177, 252]. Both groups [178, 253] synthesized the [4.4]betweenallene 606 and determined its structure by X-ray diffraction. 

Methylenecyclohexane oxide has been prepared by the oxidation of methylenecyclohexane with benzonitrile-hydrogen peroxide or with peracetic acid by treatment of 1-chlorocyclo-hexylmethanol with aqueous potassium hydroxide and by the reaction of dimethylsulfonium methylide with cyclohexanone. This reaction illustrates a general method for the conversion of ketones and aldehydes into oxiranes using the methylene-transfer reagent dimethyloxosulfonium methylide. The yields of oxiranes are usually high, and the crude products, in most cases, are of sufficient purity to be used in subsequent reactions (e.g., rearrangement to aldehydes) without further purification. 

Figure 23. Top temperature-dependent reversal of enantioselectivity for the enantiomers of (1-methyleth-yl)oxirane by complexation gas chromatography on nickel(II) bis[3-(heptafluorobutanoyl)-8-methylene-(1 /i)-camphorate]203. Bottom linear Van t Hoff plot and determination of the isoenantioselectivc temperature (89 °C).

The crucial methylenation step in this synthesis undoubtedly gave the 3,5-methylene acetal, not the 2,3-acetal (or the highly improbable 2,5-methylene acetal), because, otherwise, a 6-0-methyl-2(or 3)-0-p-tolylsulfonyl compound would have been obtained which could only have formed an epoxide (oxirane). The oxirane ring might have been opened under the conditions of the saponification the product would not then have been a dianhydride. 

The amount of EGA (the current efficiency of EGA generation) is measured in both acetone and methylene chloride-THF. Both Figs. 1 and 2 show that a sharp increase in the concentration of EGA is observed in the electrolysis of lithium, sodium, and magnesium perchlorate solution, being consistent with the result of the oxirane ring opening reaction to ketones (Table 2). 

Systematic name . 2,2 -[(1 -Methylethylidene)bis(4,1 -phcny Icncoxy methylene) bis-(oxirane)... 

Acetoxy-4,8-dimethyl-8-fluoro-9-hydroxy-13-methylene-l 2-oxo-ElOb, 142 (Oxirane + HF,)... 

Semistabilized ylides such as benzylidene- (55) or methylene- (59) triphenylarsorane reacted with carbonyl compounds in ether to give olefins as well as oxiranes. For example, reaction of methylene triphenylarsorane with benzophenone gave, besides triphenylarsine oxide... 

Reaction of benzylidene triphenylarsorane with aromatic aldehydes in alcohol afforded either arsine oxide and olefin or arsine and oxirane (97). Thus, from nitro- (58, 59, 97) or cyanobenzylidene derivatives (97) and aromatic aldehydes, trans-substituted oxiranes were obtained in 50-90% yield (97). Similarly, methylene triphenylarsorane reacted with benzal-dehyde in alcoholic solution to give triphenylarsine and phenyloxirane (49) in 87% yield (97). 

The synthetic method (c), is a base-catalysed ring opening of an oxirane.246 Since the oxirane may be formed by the epoxidation of an olefin (Section 8.1.3, p. 1132), or by a methylene insertion reaction into a carbonyl group (Section 8.1.2, p. 1131), this method is of some versatility. 

A facile synthesis of 180 with a better yield has been developed as follows. O-Deacetylation of 51 with hydrochloric acid gave DL-(l,3/2)-3-bromomethyl-5-cyclo-hexene-1,2-diol (181). Stereospecific epoxidation of 181 with mCPBA and subsequent acetylation gave-the epoxide (182), which afforded the exocyclic methylene derivative (183) by dehydrobromination with silver fluoride [51]. Reductive cleavage of the oxirane ring of 183 with lithium aluminium hydride, followed by acetylation yielded... 

Methyl-l-methylen-phospholan bzw. -phosphorinan liefem mit Oxiran oder Oxetan spirocyclische Tetraorganophosphorane14 ... 

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