Alkyl halides epoxides

E+ = alkyl halides, epoxides, carbonyl compounds, 2,/1-unsaturated carbonyl compounds... 

Enals vinyl silyl ketones.1 The anion of I reacts smoothly with va rious electrophiles (alkyl halides, epoxides, carbonyl compounds). The products are converted to (E)-enals by oxidation with 30% H202. 

Benzyl methyl ether or allyl methyl ethers can be selectively metalated at the benzylic/allylic position by treatment with BuLi or sBuLi in THF at -40 °C to -80 C, and the resulting organolithium compounds react with primary and secondary alkyl halides, epoxides, aldehydes, or other electrophiles to yield the expected products [187, 252, 253]. With allyl ethers mixtures of a- and y-alkylated products can result [254], but transmetalation of the lithiated allyl ethers with indium yields y-metalated enol ethers, which are attacked by electrophiles at the a position (Scheme 5.29). Ethers with ft hydrogen usually undergo rapid elimination when treated with strong bases, and cannot be readily C-alkylated (last reaction, Scheme 5.29). Metalation of benzyl ethers at room temperature can also lead to metalation of the arene [255] (Section 5.3.11) or to Wittig rearrangement [256]. Epoxides have been lithiated and silylated by treatment with sBuLi at -90 °C in the presence of a diamine and a silyl chloride [257]. 

Diselenides. These compounds can be prepared in satisfactory yield by reaction of 1 with alkyl halides, epoxides, or lactones in THF at 20°. 

Vinyl selenides have been lithiated at the a-position by LDA983,984 at —78 °C in THF to give a-(arylselanyl)vinyllithiums 680, a-(methylselanyl)vinyllithiums 681 being obtained by selenium-lithium transmetallation from l,l-bis(methylselanyl)alkenes with n-BuLi in THF or t-BuLi in ether at —78 °C985 986. These intermediates reacted with alkyl halides, epoxides, carbonyl compounds and DMF985, the final deprotection being performed by mercury(II) salts986. 

Metallated 1-ethoxy-1,3-dienes 697 and 712, obtained from the corresponding acetals by means of the LICKOR base, have been treated with alkyl halides, epoxides, carbonyl compounds, carbon dioxide and carboxylic esters affording ( )-l-substituted 1-ethoxy-1,3-dienes and, after hydrolysis, a,P-unsaturated carbonyl compounds1007-1010 (Scheme 186). Intermediates 697 and 712 have been transformed into the corresponding vinyl stan-nanes, which were submitted to Stille couplings with iodobenzene and benzoyl chloride823. 

How to make alkyl halides, epoxides, alcohols, and ethers through electrophilic addition... 

This chapter is devoted exclusively to the alkylation of the above mentioned organometallic reagents with alkyl halides, epoxides and oxetanes. It includes a large variety of organosulfur- and organoselen-ium-stabilized carbanions derived from saturated and unsaturated sulfides, selenides, sulfoxides, selen-oxides and sulfones as well as those carbanions bearing another heteroatomic moiety. The chapter excludes, however, those organometallics which can be viewed as a-thio and a-seleno enolates. 

Both the selenoxide and the selenonium ylide routes have been applied to cyclobutyl derivatives, themselves readily available 57) from selenoacetals of cyclo-butanones on one hand and primary alkyl halides, epoxides, or carbonyl compounds on the other. 

The selenium-stabilized carbanions formed react with a variety of electrophiles such as carbonyl compounds, alkyl halides, epoxides, etc., transforming them into several functional groups, as exemplified in Scheme 15.73 [153]. 

Lithium derivatives of allyl silanes react in the y-position with alkyl halides, epoxides, and carbonyl compounds. The lithium derivative 110 of allyl silane 109 gives only the y-adduct 111 with ketones.31 Vinyl silanes such as 111 are usually converted into carbonyl compounds via epoxides which rearrange with Lewis acid catalysis and loss of silicon to give protected versions of ketones or aldehydes 112. 

Dithians 20 illustrate this approach and have been remarkably popular considering the problems in their use. They can be made from aldehydes with propane-1,3-dithiol and Lewis acid catalysis. They are deprotonated with BuLi and react with alkyl halides, epoxides, and carbonyl compounds (E+) to give 22 and hence 19 after hydrolysis. The hydrolysis is by no means easy there are many methods and this alone should warn us that none is very good.6... 

Hydroxyl could always react with alkyl halide, epoxide and a series of halides to obtain the ester, ether and even the polymers or CCDs. An electron withdraw group is needed to activate the oxygen atom while the C-OH bond crashes. 

The above two-step reaction sequence is of unusual interest from a synthetic perspective. Note that we have converted a typically electrophilic aldehyde (carbonyl) carbon into a nucleophilic carbanion center in the 1,3-dithiane anion. The overall process thus accomplishes a polarity inversion or, to use the more popular German term, umpolung. The 1,3-dithiane anion may now be reacted with a variety of electrophiles, such as alkyl halides, epoxides, and carbonyl compounds, in what is known as the Corey-Seebach reaction ... 

Ethers are generally unreactive except with strong acids such as HI and HBr, which leads to cleavage of the ether to an alcohol and an alkyl halide. Epoxides are particularly reactive with nucleophiles, which open the three-membered ring at the less substituted carbon. Epoxides also react with an acid catalyst and weak nucleophiles such as water or alcohols, as well as with cyanide, azide, etc. 

Ethers are generally unreactive except with strong acids such as HI and HBr, which leads to cleavage of the ether to an alcohol and an alkyl halide. Epoxides are particularly reactive with... 

The orthoester (MeSe)3CH gives, with LDA, the salt (MeSe)3CLi, whose reactions with alkyl halides, epoxides, and heptanaP have been demonstrated. 

Reaction with Alkyl Halides, Epoxides, and Other Electrophiles. TrimethylsUylallyllithium reacts with alkyl halides at low temperature, giving mixtures of a- and y-(E) products in ratios that vary with the electrophile and the reaction conditions (eq 9). In these reactions the )/-(E)-alkylation product generally predominates. For example, when trimethylsilylaUyl-lithium is formed by deprotonation of allyltrimethylsilane with n-butyllithium in the presence of potassium r-butoxide in THF, the (E)-vinylsilane alkylation product is obtained in better then... 

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