Oxiranes from carbonyl compounds

Oxiranes from carbonyl compounds with CH2 fragments (ylides)... 

Preparation of Oxiranes from Carbonyl Compounds by Formation of Carbon-Carbon Bonds... 

Oxiranes from Carbonyl Compounds with CH2-equivalents (CH2N2, LiCH2X, S, Se, and As Ylides) 129... 

Syn SOI (1981) (preparation of acetals from alcohols or oxiranes and carbonyl compounds)... 

Methods for the Preparation of Acetals from Alcohols or Oxiranes and Carbonyl Compounds, Meskens, F. A J. Synthesis 1981, 501,... 

Oxiranes can be prepared in excellent yield from carbonyl compounds by alkylidene transfer with sulfonium ylides. The reaction is generally carried out with dimethylsulfonium methylide 77, dimethylsulfoxonium methylide 78, or related compounds such as anionoid species originating from sulfylimines 79 and sulfox-imines 80 that can undergo addition to the electrophilic carbonyl carbon. 

Krief et al. have shown that selenium ylides behave as their sulfur analogues and convert a variety of carbonyl compounds to oxiranes <89H(28)1203>. The latter compounds can be directly obtained by using R2Se=CHR /i-hydroxyalkylselenides (available from carbonyl compounds by addition of RSeCH2Li) may serve as suitable precursors as well, either in a two-step protocol, via the selenonium salt by alkylation with magic methyl (MeS03F), or directly by treatment with thallous ethoxide in chloroform. Oxidation of the /t-hydroxyalkylselenides with peracid, followed by treatment of the resulting selenone with base, results in oxirane formation (Scheme 60). 

Synthesis of acetals from oxiranes and carbonyl compounds 84KGS291 ... 

Until about 30 years ago, hydrazones derived from carbonyl compounds were not used in organic synthesis. They were used only for analytical purposes , and as protecting groups of aldehydes and ketones ". Corey investigated dimethylhydrazones of ketones and aldehydes with a-hydrogens, and found that they undergo deprotonation with LDA or BuLi in THF at the a-carbons to the hydrazonic moiety in 90-100% yield. The formed lithium compounds, used as enolate anion equivalents, create new carbon-carbon bonds in their reaction with different electrophiles such as alkyl halides or oxiranes, ketones and aldehydes (equation 21). 

As imido esters, dihydro-1,3-oxazines of type 14 display reactivity similar to 2-oxazolines (see p 135). The a-C-H bonds of the 2-alkyl group are CH-acidic. They are metalated by reaction with butyllithium and then undergo C-C forming reactions with electrophiles such as haloalkanes, oxiranes or carbonyl compounds. The dihydro-1,3-oxazines 16, which are obtained from 15 by a-metalation and alkylation, undergo reduction with NaBH4 forming 17. Acid hydrolysis cleaves the cyclic aminal function of 17 yielding aldehydes 18 ... 

Metalation of dimethylhydrazone derivatives of aldehydes and ketones occurs cleanly. Unsymmetrical ketones suffer proton abstraction from the lesser-alkylated a-carbon atom specifically, and the a-lithiated dimethylhydrazones react more vigorously than the corresponding enolates with halides (Scheme 23), oxirans, and carbonyl compounds (Scheme 23). Cuprate derivatives can be obtained from the lithiated species in the usual manner and the cuprates undergo Michael addition to ajS-unsaturated ketones. 

The addition of acetylides to oxiranes yields 3-alkyn-l-ols (F. Sondheimer, 1950 M.A. Adams, 1979 R.M. Carlson, 1974, 1975 K. Mori, 1976). The acetylene dianion and two a -synthons can also be used. 1,4-Diols with a carbon triple bond in between are formed from two carbonyl compounds (V. Jager, 1977, see p. 52). The triple bond can be either converted to a CIS- or frans-configurated double bond (M.A. Adams, 1979) or be hydrated to give a ketone (see pp. 52, 57, 131). 

Reaction of the carbanion of chloromethyl phenyl sulphoxide 409 with carbonyl compounds yields the corresponding 0-hydroxy adducts 410 in 68-79% yield. Each of these compounds appears to be a single isomer (equation 242). Treatment of adducts 410 with dilute potassium hydroxide in methanol at room temperature gives the epoxy sulphoxides 411 (equation 243). The ease of this intramolecular displacement of chloride ion contrasts with a great difficulty in displacing chloride ion from chloromethyl phenyl sulphoxide by external nucleophiles . When chloromethyl methyl sulphoxide 412 is reacted with unsymmetrical ketones in the presence of potassium tcrt-butoxide in tert-butanol oxiranes are directly formed as a mixture of diastereoisomers (equation 244). a-Sulphinyl epoxides 413 rearrange to a-sulphinyl aldehydes 414 or ketones, which can be transformed by elimination of sulphenic acid into a, 8-unsaturated aldehydes or ketones (equation 245). The lithium salts (410a) of a-chloro-/ -hydroxyalkyl... 

Method B (polymer-supported) The aldehyde or ketone (1.4 mmol) is added to S,S-dimethyl polystyrylsulphonium fluorosulphonate (2 g) suspended in CH2CI2 (15 ml) and the mixture is stirred with aqueous NaOH (65%, 2 ml) and TBA-I or TBA-OH (0.6 mmol) until the carbonyl compound has been consumed. The filtered solution is extracted with H,0 (3 x 25 ml) and evaporated to yield the oxirane (e.g. from PhCHO,... 

Interestingly, sulfonium ylides generated from electrophilic carbene complexes and sulfides can react with carbonyl compounds, imines, or acceptor-substituted alkenes to yield oxiranes [1320-1325], aziridines [1321,1326,1327] or cyclopropanes [1328,1329], respectively. In all these transformations the thioether used to form the sulfonium ylide is regenerated and so, catalytic amounts of thioether can be sufficient for complete conversion of a given carbene precursor into the... 

All acetylenes with a terminal triple bond are instantaneously converted into the alkali acetylides by alkali amides in liquid ammonia. For many alkylations with primary alkyl halides liquid ammonia is the solvent of choice and the functionalization with oxirane can also be carried out in it with good results. Reactions of ROOM with sulfenyladng agents (R SSR1, R SON, R SSC R ) or elemental sulfur, selenium or tellurium are mostly very successful in ammonia, the same holds for the preparation of ROC1 from RC=CM and iodine. The results of couplings with carbonyl compounds are very variable. 

Both the alio and manno epoxides (9) or (7), or their debenzyliden-ated analogs, undergo oxidation with methyl sulfoxide and boron trifluoride,104 but, unlike 5,6-anhydrohexofuranose derivatives (see p. 163), they do not yield a simple a-hydroxy carbonyl compound, as would be expected by analogy with simple oxiranes instead, the rearranged diulose (46) is obtained in low yield, possibly by elimination of methanol from the intermediate (47). 

Metallated polystyrenes are versatile intermediates for the preparation of a number of polystyrene derivatives. Metallated polystyrene has been prepared from haloge-nated polystyrenes by halogen-metal exchange [41,42,65,66] and by direct metallation of polystyrene [67-69] (see Chapter 4). Electrophiles suitable for the derivatization of metallated polystyrene include carbon dioxide, carbonyl compounds, sulfur, trimethyl borate, isocyanates, chlorosilanes, alkyl bromides, chlorodiphenylphosphine, DMF, oxirane, selenium [70], dimethyldiselenide [71], organotin halides [69], oxygen [72], etc. [41,42,65-67],... 

A one-pot procedure combines the generation of trimethylsulfonium hydrogensulfate (Me3S HS04 ) from dimethyl sulfide, sulfuric acid and methanol, and its use in situ for oxirane formation with carbonyl compounds [451] (Table 4.5). 

The formation of an oxirane from the reaction of dimethylsulfonium methylide with conjugated carbonyl compounds was applied to... 

As discussed in section 4, reaction of the peroxy radicals with N02 gives thermally unstable peroxy nitrates. Reaction with H02 gives hydroperoxides and possibly carbonyl compounds. Reaction with other peroxy radicals (R 02) gives alkoxy radicals, carbonyls, and alcohols. The alkoxy radicals will then either isomerize, react with 02, or decompose (see Sect. 3). Thus, the NO3 radical-initiated atmospheric degradation of alkenes leads to oxiranes (generally in small yield), nitrooxy hydroperoxides, nitrooxy carbonyls, and nitrooxyalcohols. For a detailed listing of products from individual alkenes the reader should consult Calvert et al. [55]. 

---