Alkenes to epoxides

Transition-metal atoms have been shown to deoxygenate epoxides to alkenes (36). Chromium and titanium atoms emerged as the most effective species in this regard, abstracting over two equivalents of oxygen. By studying the reaction of a wide range of epoxides with chromium atoms, the reaction... [Pg.162]

A useful complement to the known methods for the deoxygenation of epoxides to alkenes is the reaction of epoxides with alkali (7,0-diethyl phosphorotellurolates. - ... [Pg.128]

Divalent chromium reduces triple bonds to double bonds (trans where applicable) [195], enediones to diones [196], epoxides to alkenes [192] and aromatic nitroso, nitro and azoxy compounds to amines [190], deoxygenates amine oxides [191], and replaces halogens by hydrogen [197,198],... [Pg.30]

Epoxides (oxiranes) can be reduced in different ways. So-called deoxygenation converts epoxides to alkenes. Such a reaction is very useful since it is the reversal of epoxidation of alkenes, and since both these reactions combined represent temporary protection of a double bond. [Pg.83]

More frequent than the deoxygenation of epoxides to alkenes is reduction of epoxides to alcohols. Its regiospecificity and stereospecificity depend on the reducing agents. [Pg.83]

Reductions with Sml2. Sml2 (2 equivalents) can be used to reduce sulfoxides to sulfides (80-90% yield) and to convert epoxides to alkenes (65-90%). Ybl, is somewhat less effective in these reductions. [Pg.344]

Stereoselective deoxygenation of epoxides. The ate complex [Bu3SnAl-(CH3)3] Li+ (1) formed from Bu3SnLi and A1(CH3)3 converts epoxides to alkenes with overall retention of stereochemistry. The results can be explained by inversion in the epoxide cleavage and antf-elimination of the Bu3Sn and O A1(CH3)3 groups. Example ... [Pg.320]

Deoxygenation. This substance reduces epoxides to alkenes in 85-95% yield, generally with retention of configuration, particularly in reduction of trans-tpox-ides. This reduction proceeds more readily than that of carbonyl or ester groups, but a,(3-enals are coupled reductively by 1 at 25° to diallylic ethers. [Pg.120]

Samarium iodide has also been used for reducing epoxides to alkenes. Compared with other low-valent metal systems this reagent requires prolonged reaction time at room temperature, but the stereoselectivity, with c -epoxides giving m-alkenes, is high. " ... [Pg.889]

Vapor-deposited carbon atoms have been known to reduce epoxides to alkenes but with low stereoselectivity, whereas chemically generated carbon atoms, by thermal decomposition of S-tetrazolediazo-nium chloride (2), deoxygenate cis- and franr-2-butene oxide with a high degree of retention of stereochemistry. ... [Pg.890]

The release of ring strain in epoxides is probably responsible for the high reactivity of these special ethers. HI opens epoxides under mild conditions stereospecifically to iodohydrins (Scheme 26). The mechanism is similar to the reaction of bromide with epoxides (see Section 1.7.3.3). It should be noted, however, that reduction of epoxides to alkenes may occur if vicinal diiodides are intermediately formed, which can lose I2 under the reaction conditions. With the combination of acyl chloride and Nal unstable diiodides are avoided and 2-iodoethyl esters are formed from oxiranes (Scheme 27). ° ... [Pg.215]

The thermal instability of the telluriranes is also utilized in the transformation of epoxides to alkenes <77CC658, 80JOC2347). When epoxides are treated with sodium 0,0-diethyl phos-... [Pg.268]

Epoxides — olefins This reagent (1) can convert epoxides to alkenes in 50-98% yield. The reaction requires three equivalents of 1, and the cw-configuration of the sub.strate is not retained. [Pg.392]

A stereospecific method for deoxygenating epoxides to alkenes involves reaction of the epoxide with the diphenylphosphide ion, followed by methyl iodide. The method results in overall inversion of the alkene stereochemistry. Thus,... [Pg.69]

Finally, deoxygenation of epoxides to alkenes represents an important transformation in organic chemistry. In this regard, MeRe03 was reported to catalyze deoxydehydration of epoxides to alkenes by employing primary and secondary alcohols in benzene as the solvent (14TL4178). Likewise, a... [Pg.70]

Triphenylphosphine can be used to convert epoxides to alkenes—for example, 0... [Pg.751]

Scheme 19.2S General mechanistic pathway of the. Tnlia-Kocienski olefination. Scheme 19.26 Conversion of epoxides to alkenes related to Julia-Kociensld...

Srhpiup iQ.2fi Conversion of epoxides to alkenes related to Julia-Kocienski olefination. [Pg.770]

New phosphorus-based deoxygenating agents include P2I4, which reduces epoxides to alkenes, besides dehydrating aldoximes to nitriles, and Ph3Pl2 and (Me2N)3P-l2-NaI which reduce sulphoxides to sulphides. ... [Pg.221]

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