Copper epoxide ring opening

Scheme 5.7 illustrates these and other applications of the hydride donors. Entries 1 and 2 are examples of reduction of alkyl halides, whereas Entry 3 shows removal of an aromatic halogen. Entries 4 to 6 are sulfonate displacements, with the last example using a copper hydride reagent. Entry 7 is an epoxide ring opening. Entries 8 and 9 illustrate the difference in ease of reduction of alkynes with and without hydroxy participation. 

Thioacetals eliminate to vinylsulfides in the presence of CuOTf (Scheme 46).192 Cu1 and Cu11 triflates are mild Lewis acids for Friedel-Crafts acylation and alkylation reactions. CuOTf effectively catalyzes the reaction of anisole with selenoesters.193,194 Copper(II) sulfate promotes epoxide ring opening reactions in the presence of pyridine,195 with retention of configuration being observed. Cu(OTf)2 is a catalyst for the ring opening of aziridine by aniline.196... 

Starting with a copper catalyzed epoxide ring opening, using phenyl magnesium chloride, a secondary alcohol was generated, which in turn was transformed into an electrophile by tosylation (Scheme 29). The tosylate 117... 

Several types of copper-loaded polymer have been prepared. Hydrocarbon spacers were introduced between polystyrene and copper (23). Six synthetically useful copper-promoted reactions including a Diels-Alder reaction, an epoxide ring-opening, and an aryl iodide hydrolysis were examined by using the polymeric catalyst [34]. Use of the copper-loaded polymers often either improved the yield or reduced the reaction time compared with those for conventional copper salts. 

Epoxide ring opening of 484c with -nonylmagnesium bromide in the presence of copper(I) bromide provides in 77% yield the alcohol 489, which is transformed into (+ )-(77 ,8 S)-disparlure (490), the sex pheromone of the gypsy moth Porthetria dispar [159]. 

Lithium or copper enolates, generated in situ by conjugate reduction of afi-unsaturated ketones, may be trapped by MeSSMe, PhSSPh, or PhSCl to give the /S-ketosulphide. /3-Keto-sulphides and -selenides are available on chloral-alumina oxidation of the corresponding /3-hydroxy compounds. The latter compounds may be prepared by alumina-promoted epoxide ring opening by thiols and selenols (Scheme 16). ... 

Boningari, T., Ohnos, A., Reddy, B. M., Sommer, J., and Pale, P. 2010. Zeo-click chemistry Copper(I)-zeofite-catalyzed cascade reaction one-pot epoxide ring-opening and cycloaddition. Eur. J. Org. Chem. 2010(33) 6338-6347. 

Asymmetric ring-opening of saturated epoxides by organoctiprates has been studied, hut only low enantioselectivities f -c 1596 ee) have so far been obtained [49, 50]. Muller et al., for example, have reported that tlie reaction between cyclohexene oxide and MeMgBr, catalyzed by 1096 of a chiral Schiffhase copper complex, gave froiis-2-metliylcyclohexanol in 5096 yield and with 1096 ee [50]. 

Asymmetric microbial oxidation afforded the (-)-epoxide which has been explored as a building block ring opening reactions with organometallic nucleophiles, and via Friedel-Crafts reactions have been reported. [226,227]. A non-biotransformative approach to this epoxide has also been described [228]. Copper(II)-catalysed oxidative hydrolysis (Eq. 72) affords a lactic acid analogue in high enantiomeric purity [229]. 

Perfluoroalkylated epoxides as representatives of alicyclic ethers are successfully oxidized152 directly to a-hydroxycarboxylic acids 5 despite the fact that the epoxides 4 are protonated and subsequently hydrolyzed with difficulty. It has been found that the tandem ring opening/oxi-dation reaction is accomplished by concentrated nitric acid152 in the presence of copper ions in the mixture.181... 

Chiral all-syn-l,3-polyols. A reiterative route to these polyols from an optically active epoxide (1) involves ring opening with a cuprate derived from vinyllithium and copper(I) cyanide (11, 366-367) to give an optically active homoallylic alcohol (2). This is converted into the fepoxide (4) via a cyclic iodocarbonate (3) by a known procedure (11, 263). Repetition of the cuprate cleavage results in a homoallylic 1,3-diol (5). The ratio of desired syn- (o anfi-diols is 10-15 1. This two-step sequence can be repeated, with each 1,3-diol unit formed being protected as the acetonide. The strategy is outlined in Scheme (I). 

Copper-catalyzed asymmetric allylic alkylations with organometalUc reagents used for small-ring openings, such as epoxides and aziridines, have gained interest. Illustrating... 

Copper-mediated sulfide elimination can lead to ring opening reactions. The hydroxy thioacetal 83, when treated first with n-BuLi and then with CuOTf afforded 84 in 92 % yield via a Grob fragmentation (Sch. 21) [47]. Two equivalents of the Lewis acid were required for the reaction because one equivalent complexes the alk-oxide and a second is necessary to activate the sulfide for elimination. Ring enlargement occurred upon treatment of 85 with CuOTf in benzene through the intermediacy of the thio-substituted epoxide 86 [48]. a-Phenylthiocyclohexanone 87 was obtained in 83 % yield. 

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