Alkylation aryl epoxides

Vinylic sulfides containing an a hydrogen can also be alkylated by alkyl halides or epoxides. This is a method for converting an alkyl halide RX to an a,P unsaturated aldehyde, which is the synthetic equivalent of the unknown HC=CH—CHO ion. Even simple alkyl aryl sulfides RCH2SAr and RR CHSAr have been alkylated a to the sulfur. ... 

Aryl and alkyl hydroxylations, epoxide formation, oxidative dealkylation of heteroatoms, reduction, dehalogenation, desulfuration, deamination, aryl N-oxygenation, oxidation of sulfur Oxidation of nucleophilic nitrogen and sulfur, oxidative desulfurization Oxidation of aromatic hydrocarbons, phenols, amines, and sulfides oxidative dealkylation, reduction of N-oxides Alcohol oxidation reduction of ketones Oxidative deamination... 

Peroxidases have been used very frequently during the last ten years as biocatalysts in asymmetric synthesis. The transformation of a broad spectrum of substrates by these enzymes leads to valuable compounds for the asymmetric synthesis of natural products and biologically active molecules. Peroxidases catalyze regioselective hydroxylation of phenols and halogenation of olefins. Furthermore, they catalyze the epoxidation of olefins and the sulfoxidation of alkyl aryl sulfides in high enantioselectivities, as well as the asymmetric reduction of racemic hydroperoxides. The less selective oxidative coupHng of various phenols and aromatic amines by peroxidases provides a convenient access to dimeric, oligomeric and polymeric products for industrial applications. 

A regioselective and highly syn-stereoselective catalyst-free intermolecular alkylation of aryl borates with aryl epoxides under mild, neutral conditions has been reported.27 The reaction of /ra .s-stilbene oxide with tri(3,5-dimethylphenyl)borate gave a 38% yield (>95% syn) of the C-alkylated product (13), easily separated from (g) the O-alkylated product(s). Triflic anhydride has been used to activate enones to nucleophilic attack by electron-rich arenes in the presence of a sterically hindered base.28 Resorcinol dimethyl ether, for example, reacted with cyclohex-2-en-l-one to... 

The cyclization in Step B is an improvement of Butler s procedure for the synthesis of which employs less convenient reagents, KNH and l-bromo-3-chloroacetone acetal. Beside the acetals derived from neopentyl glycol, those derived from ethanol, 1,3-propanediol and 2,4-pentanediol have been synthesized by the present method. The second part of Step B involves the formation and the electrophilic trapping of cyclopropenyl anion 2, which is the key element of the present preparations. Step B provides a simple route to substituted cyclopropenones, but the reaction is limited to alkylation with alkyl halides. The use of lithiated and zincated cyclopropenone acetal, on the other hand, is more general and permits the reaction with a variety of electrophiles alkyl, aryl and vinyl halides, Me3SiCl, Bu3SnCl, aldehydes, ketones, and epoxides. Repetition of the lithiation/alkylation sequence provides disubstituted cyclopropenone acetals. 

Suitable cleaving agents include organic halides such as primary alkyl bromides, iodides or sulfo-nates " ° allylic," - allenic and propargylic bromides vinylic or aryl halides with nickel or palladium promoters " alkyl chloroformates epoxides and even cyanogen or cyanogen bromide. Typical examples of such couplings are depicted in equations (55)-(57). 

Of the alkylation systems described in Section 1.1.2.5.1, the DEAD-PhsP procedure cannot be used in the preparation of acyclic dialkyl ethers, but alkyl aryl ethers and cyclic ethers have been synthesized. The PhaP-CCU system is also effective for the cyclodehydration of 1,4- and 1,2-diols to tetrahydrofurans and epoxides, respectively. ... 

R = alkyl, aryl R = 1° or 2 alkyl, allyl, benzyl, activated aryl, acyl X - Cl, Br, I, OTs electrophile epoxide, dialkyl sulfate, alkyl sulfonate, alkyl nitrate base = NaOR NaH base = KOf-Bu, cone. NaOEt, NaH solvent = R OH, f-BuOH, benzene, ether, DMF... 

In Pd(0)-catalyzed isomerization reaction of epoxides, alkyl-substituted epoxides afford methyl ketones (path a, Scheme 11), whereas aryl-substituted epoxides give aldehydes or ketones via cleavage of the benzylic C-O bond (path b) [94]. 

Figure 2. Rearrangement of styrene epoxides (R = alkyl, aryl, haloalkyl, alkoxy, alkylthio).

A shortcoming of these materials is their hydrophilicity, which means they are ineffective catalysts for epoxidations with hydrogen peroxide strong adsorption of water on the hydrophilic surface severely limits access of hydrophobic substrates to the active site. Hence, much effort has been devoted to the synthesis of hydrophobic analogs by polycondensation of a titanium(IV) alkoxide with RSi(OEt)3 (R = alkyl, aryl) instead of Si(OEt)4 [23,24,40]. 

Diones. Alkyl aryl ketones (1) can be converted into acyl-a, a -dichloro-alkyl ketones (2) by conversion to a ketimine (a) followed by chlorination with NCS in CCU ct,o-dichloro ketojtes (2) are obtained on hydrolysis. When treated with sodium methoxide in methanol 2 is converted into a mixture of the isomers 3 and 4 (probably through an epoxide intermediate). Both isomers are converted into a-aryl-l,2-diones (5) on acid hydrolysis. Overall yields vary from 72 to 84% when all intermediates are isolate, but are somewhat higher when the reaction is carried out as a one-pot operation. ... 

N-Alkylations (arylations) of tetrazoles are continuously reported, however regioselectivity is problematic with substrates containing other reactive azole centers. The combination of alcohols or epoxides, activated with either zinc triflate or dibenzyl N,N-diethylphosphoramidate, in acetonitrile, nitromethane or dichloromethane alkylates... 

The most important costabilizers in PVC formulations used mainly in combination with mixed metal salts are alkyl-aryl-phosphites to improve early color. Epoxy compounds, for example, epoxidized fatty esters such as epoxidized soy bean oil, react directly with HCl or substitute labile chlorine atoms, for example, in the presence of zinc ions. Furthermore, the epoxidized fatty esters act as plasticizers. Polyols such as pentaerythritol or dipentaerythritol and P-diketones act as complexing agents and deactivate the negative effect of the formed zinc chloride. Hydrotalcites... 

The reaction of CO2 with a metal hydride produces formate complexes M-0C(0)H, not formyl derivatives M-C(0)0H, and the insertion into M-C bonds gives the appropriate carboxylate compounds M-0C(0)R. In a similar fashion, the reactions with M-OH and M-OR (R = alkyl, aryl) generate the corresponding bicarbonate M-0C(0)0H and carbonate M-0C(0)0R species, respectively. The reaction of CO2 with a zinc hydroxide moiety is particularly important in biological systems, namely, for the reversible hydration of CO2 to HCOs catalyzed by Zn(ll) in carbonic anyhdrases. Moreover, it has been postulated that the insertion of CO2 into M-O bonds is essential in the co-polymerization of CO2 and epoxides and in the preparation of cyclic carbonates and polycarbo-In a similar vein, the insertion of CO2 into the M-N bond of both main group and transition metal... 

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