Epoxides with phosphines

Synthesis of azindines Irom epoxides via amino alcohols or azido alcohols and reaction with phosphines or phosphites... 

Butyne-l,4-diol has been hydrogenated to the 2-butene-diol (97), mesityl oxide to methylisobutylketone (98), and epoxides to alcohols (98a). The rhodium complex and a related solvated complex, RhCl(solvent)(dppb), where dppb = l,4-bis(diphenylphosphino)butane, have been used to hydrogenate the ketone group in pyruvates to give lactates (99) [Eq. (15)], and in situ catalysts formed from rhodium(I) precursors with phosphines can also catalyze the hydrogenation of the imine bond in Schiff bases (100) (see also Section III,A,3). 

Niobia-supported MTO has been prepared either by the deposition of sublimed MTO onto the support, or by the impregnation of the support by a solution of MTO, and has been well characterised [54]. A large variety of oxidation reactions were efficiently performed with niobia-supported MTO, such as olefin metathesis catalysis [53,54], reactions of ethyl diazoacetate, heteroatom oxidation (amine and phosphine oxidations) and olefin epoxidation with hydrogen peroxide [55] (Scheme 13). 

At low temperatures dioxetane adducts with trivalent phosphorus have been isolated by Bartlett and coworkers. These cyclic phosphoranes gradually decompose to give the corresponding epoxide and phosphine oxide (Scheme 39) (73JA6486). Aryl-substituted phosphines... 

There have been extensive studies on the reaction of dioxetanes and dioxetanones with nucleophiles (C, N, P, and S) and the reader is directed to CHEC-II(1996) for an exhaustive list up to 1996. The most common reactions of dioxetanes have been with phosphorus nucleophiles. The phosphines and phosphites first insert into the 0-0 bond. The phosphorane intermediate then collapses to afford phosphine oxide or the trialkylphosphate and the corresponding epoxide (Scheme 6). The same is true for the treatment of a-peroxy lactones with phosphines and phosphites except that the so-formed a-lactone intermediate undergoes decarboxylation and ultimately furnishes a ketone <1997JOC1623>. 

Epoxides can be formed by treatment with phosphines [133a] via the corresponding phosphorane 138 (Sch. 78) [133b], and analogous reactions... 

Many other reports of ligand libraries for specific catalytic applications have been reported. Among them, Gilbertson and co-workers reported a chiral phosphine library, tested in the rhodium-catalyzed asymmetric hydrogenation of an enamide (158,159), and a similar library for the palladium-catalyzed allylation of malonates (160, 161) Hoveyda and co-workers (162, 163) reported a chiral Schiff base library, screened in the titanium-catalyzed opening of epoxides with (TMSCN) (trimethyl silyl cyanide) ... 

Besides zinc, copper and nickel, numerous other transition metals show high activity in epoxide carboxylaiion, excellent catalysts being chromium, manganese, iron or cobalt compounds in the presence of organic halides 1227). Halides of ruthenium, rhodium or cadmium were also used with phosphines to accelerate the reaction velocity (210). Kisch found catalyst systems which are active, eip-en at room temperature and under ordinary pressure [228]. Tlie most cftective catalyst was the combination of triphenylphosphine and molybdenum pcntachloridc propylene carbonate was formed in a 78% yield. 

Ring opening of epoxides using selenolates that are generated by other methods, such as reduction with samarium reagents [19], electrochemical reduction [22], reduction with phosphine [25] or reduction with NaBH4 under microwave irradiation [34], have also been reported. 

One of the earliest chemical transformations of 1,2-dioxetanes was their reaction with phosphines (Eq. 72). It was shown that the trivalent phosphorus first inserts into the peroxide bond to afford a relatively stable phosphorane. On warming the phosphorane eliminates phosphine oxide to yield the epoxide product. In this elimination, there is inversion of the stereochemistry at one of the carbon centers. 

More recently, Alexakis [32] reported the diastereoselective syn- or anti-opening of propargyl epoxides, with good to excellent 8 2 selectivity. Addition of two equivalents of phosphine as a ligand can influence the stereochemistry of the elimination step to afford either the syn- or anti-product, as shown in Eq. (73) and Table 19. 

Warren and coworkers have described the alkylation of (diphenylphosphinoyl)alkyllithiums with epoxides as an effective means of synthesizing 3-(diphenylphosphinoyl) ketones, homoenolate anion equivalents. The treatment of the adducts of lithiated phosphine oxides and epoxides with base to form cyclopropanes was reported by Toscano et al ... 

Some isomers of alkenes are particularly difficult to make and a stereospecific method is required. Fortunately there is a good one. C/.v-cyclo-octene Z-284 is easy to make by elimination and is available commercially. The epoxide 285 is made without change of stereochemistry and opening this epoxide with the very nucleophilic Ph2PLi ensures one inversion in the formation of the phosphine 286. 

Dioxetanes can also be transformed into 1,2-diols by reduction with LiAlH4 or into epoxides by treatment with phosphines in the dark.1421... 

Thiiranes can be prepared by cyclisation of 2-halo-thiols, but the most common method is via reaction of an epoxide with thiocyanate, thiourea, a phosphine sulfide or with dimethylthioformamide. ... 

Epoxides. Reaction pathways for the Mitsunobu reaction to convert l,l-diaryl-2-phenylethanediols to epoxides are phosphine-dependent. Retention of configuration at the secondary carbinolic center is observed in reaction mediated by PhsP-DIAD, while mote electron-rich phosphines (e.g., BU3P) favor products with inversion of configuration. ... 

Nucleophilic Attack at Halogen. Further studies have been reported of the reactions of diols with the triphenylphosphine-carbon tetrachloride reagent. It has now been applied to 1,2-diols (in the presence of potassium carbonate) to form epoxides and to the trans-6 o (84), the nature of the product depending on the relative amounts of phosphine and diol present. The major product of reactions involving equimolar quantities of phosphine and diol is (85). The cyclodehydration product (86) is formed in only poor yield. In the presence of carboxylic acids, the triphenylphosphine-carbon tetrachloride system causes ring-opening of epoxides with the formation of c -enol esters, the reaction presumably proceeding via nucleophilic attack by the oxirane at an acyloxyphos-phonium intermediate. ... 

---