Reactions with epoxides alkylation

Sn2 substitution reactions of alkyl halides with hard nucleophiles such as alkyl anions can be achieved most readily with the aid of organocopper chemistry [95]. Sn2 reactions with epoxides and aziridines are also synthetically useful [96]. The... 

The carboxymethylation of sucrose can be achieved by reaction with sodium chloroacetate in water or water-2-propanol mixtures in basic medium. In this case, a similar regioselectivity is observed as for the reaction with epoxides or alkyl halides with major substitutions at secondary positions, notably at OH-2.80 Cyanoethylated sucrose derivatives and the corresponding carboxylated compounds were also prepared.81... 

Alkyl halides (particularly bromides) undergo oxidative addition with activated copper powder, prepared from Cu(I) salts with lithium naphthalenide, to give alkylcopper species10. The alkyl halides may be functionalized with ester, nitrile and chloro functions ketone and epoxide functions may also be tolerated in some cases11. The resulting alkylcopper species have been shown to react efficiently with acid chlorides, enones (conjugate addition) and (less efficiently) with primary alkyl iodides and allylic and benzylic bromides (equations 5 and 6). If a suitable ring size can be made, intramolecular reactions with epoxides and ketones are realized. 

The reactions with epoxides occurred at 0° producing 2-trimethylsiloxyalkyl phenyl tellurium derivatives. The ring opening is stcrcospccific in favor of rraws-siloxy tellurium compounds and regiospecific in favor of primary alkyl tellurium compounds2. 

Two previous studies (Moser et al., 2007, 2006) explored the effects of synthetic compounds with hydrocarbon tail-group structures resembling those of FAME with attached bulky moieties on the CP and PP of SME. These studies examined novel fatty ethers made from the reaction of various alcohols (C2—Cm) with epoxidized alkyl oleates in the presence of sulfuric acid catalyst. Bulky esters (isopropyl and isobutyl) were chosen to further enhance the low temperature fluidity of the synthetic adducts produced. As the chain length of the ether moiety attached to the fatty backbone increased in length, a corresponding improvement in low temperature performance was noticed. Although the materials had improved low temperature properties over that of neat SME, none of the synthesized compounds demonstrated effectiveness in decreasing CP or PP when added to SME. 

Aryl borates can provide both C-alkylation and O-alkylation products upon reaction with epoxides <07JOC7761>. The reaction shown below exemplifies a general reaction of arylborates with vinyl epoxides <07SL3011>. A number of examples were reported, the yield shown is typical. The ratio of SN2 to SN2 is generally >95 5 and the ratio of C-alkylation O-alkylation is also excellent (usually >95 5). 

Carbon-centered nucleophiles can also be used to advantage in the reaction with epoxides. For example, the lithium enolate of cyclohexanone 96 engages in nucleophilic attack of cyclohexene oxide 90 in the presence of boron trifluoride etherate to give the ketol 97 in 76% yield with predominant syn stereochemistry about the newly formed carbon-carbon bond <03JOC3049>. In addition, a novel trimethylaluminum / trialkylsilyl triflate system has been reported for the one-pot alkylation and silylation of epoxides, as exemplified by the conversion of alkenyl epoxide 98 to the homologous silyl ether 99. The methyl group is delivered via backside attack on the less substituted terminus of the epoxide <03OL3265>. 

The combined use of catalytic amounts of N-benzylquininium chloride (1) with hydroxide bases (NaOH or KOH) has been explored for a variety of phase transfer reactions, including epoxidations, alkylations, and Michael reactions. The degree of stereoselectivity in product formation induced by the reagent can vary widely. ... 

Although reactions with epoxides proceed with a similar stereochemical outcome to that of the alkylation reaction, the deuteration (DjO), and carbonation" reactions occur predominantly with opposite stereochemistry. 

This sequence illustrates the use of enolates from 1,3-dicarbonyl compounds in Michael reactions they are useful too in alkylations, aldol condensations (Knoevenagel conditions), and reactions with epoxides, as in the synthesis3 of 20. Nowadays they tend to be used if they are readily available, or if the disconnections suggest their use, as in the building of 11 into 18. Examples include the diketone 11 and the six-membered equivalent both used in steroid synthesis, acetoacetates 16 and 19 and the keto-lactones 20, malonic acid 21 and its esters, "Meldrum s acid 22, a very enolisable malonate derivative,4 and the keto-ester 25 formed via its stable enolate 24, by the cyclisation of the diester 23, an intermediate in nylon manufacture. The compounds 11,16, 19, 20 R=H, 21, 22, and 25 are all available commercially. 

Reactions alkylations, reactions with epoxides and aldehydes, conjugate additions Heterocyclic synthesis with allyl silanes Reactions with Co-stabilised cations An Allyl Dianion The Role of Tin in Anion Formation Halide Exchange with Chelation Indium Allyls Allyl Anions by Deprotonation The synthesis ofall-trans dienes The synthesis ofall-trans retinol... 

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