Oxyalkyl groups

Acyclic ethers undergo partial j8-scission with formation of carbonyl and alkyl derivatives. Thus with ethyl ether the introduction of the oxyalkyl group is accompanied by appreciable quantities of ethyl and acetyl derivatives, attributed to jS-scission of the a-oxyalkyl radical [Eq. (47)]. 

Fig. 6. Summarization of results correlating inhibition efficacy (piso) and toxicity (log LD50) for some OP and nerve agents. Equation y = 9.87 — 1.26x p < 0.01 rxy = —0.9489. The lines indicate experimentally determined piso (human brain AChE) values (axe y) or extrapolated values (axe x) of LD50 for systox and VX. Each point represents the value of piso corresponding to LD50 value for rabbit, rat, guinea pig, mouse, and dog. The compounds under code are designated by the abbreviation of the oxyalkyl group on the phosphorus head, and by the alkyl on the nitrogen atom - e.g. VX is designated as Et-iPr (modified from B11, B14 and P3).

Thus, Yamamoto developed the Pt(II)-catalyzed migratory cydoisomerization, namely carboalkoxylation, of o-alkynylphenyl acetals 22 leading to the synthesis of 2,3-disubstituted benzofurans 23, where the former phenolic substituent resides at the C3-site (Scheme 9.9) [98, 99]. It was demonstrated that this Pt(II)-catalyzed cydoisomerization could be applied to substrates with a variety of alkynyl substituents, providing the corresponding benzofurans in moderate to excellent yields. In addition, different migrating oxyalkyl groups, such as 1-ethoxyethyl, MOM, BOM, and TBS-oxymethyl, can be effectively incorporated into this cascade transformation. 

The ortho ester modification of the Claisen rearrangement allows carboalk-oxyalkyl groups to be introduced.A mixed ortho ester is formed as an intermediate which undergoes sequential elimination and rearrangement. 

Reaction of olefin oxides (epoxides) to produce poly(oxyalkylene) ether derivatives is the etherification of polyols of greatest commercial importance. Epoxides used include ethylene oxide, propylene oxide, and epichl orohydrin. The products of oxyalkylation have the same number of hydroxyl groups per mole as the starting polyol. Examples include the poly(oxypropylene) ethers of sorbitol (130) and lactitol (131), usually formed in the presence of an alkaline catalyst such as potassium hydroxide. Reaction of epichl orohydrin and isosorbide leads to the bisglycidyl ether (132). A polysubstituted carboxyethyl ether of mannitol has been obtained by the interaction of mannitol with acrylonitrile followed by hydrolysis of the intermediate cyanoethyl ether (133). 

Different reactivity of a-oxyalkyl and boryloxyalkyl fragments was revealed in reactions with amines of weak basicity. For example, in the reaction with diphenylamine or o-aminobenzoic acid with a reagent ratio of 1 1, substitution of the oxymethyl group by the aminomethyl one takes place [Eq. (117)]. The P,B-containing heterocycle is retained (89IZV1340). 

Fmoc-Rink-Nle-pMeBHA-resin (1 g, 0.55 mmol g ) was swollen for 1.5 h in NMP in a reaction vessel equipped with a sintered glass bottom, and placed on a shaker. The Fmoc group was removed with 20% piperidine in NMP (8mL, 2 x 15 min) and after washing with NMP (8mL, 5 x 2 min), the Fmoc removal was monitored by the ninhydrin Kaiser test. Coupling of building blocks such as iV -Fmoc-/Va>-carb-oxyalkyl(OAl)Xaa-OH or /V -Fmoc-/V" -aminoalkyl(Aloc)Xaa-OH, or N -alkylated amino acids such as... 

No data has yet been published on the quantitative ratio of each degradation product. However, radiolysis should lead to lower amounts of acidic compounds than malonamides, because of the absence of any alkyl (or oxyalkyl) chain between the two amide groups. 

Carbamoyl and a-N-amidoalkyl radicals can be easily obtained by hydrogen abstraction from formamides and N-alkylamides. They have a close analogy with acyl and a-oxyalkyl radicals. The nucleophilic character of the carbamoyl radical is explained by the fact that it can be considered an acyl radical in which the alkyl or aryl group is substituted by an amino group it can be related with resonance structures like 16... 

Ab initio calculations of Giese [17] and Houk [18] have demonstrated that the geometry of the H-abstraction reaction by a-oxyalkyl radicals 46 resembles that of a nucleophilic addition to a carbonyl group 47. 

This similarity of transition state geometries of oc-oxyalkyl radicals and carbonyl groups suggests that the Felkin-Anh rule should be applicable also in radical chemistry. This is actually the case. The transition state 50A of chiral radical 50 is about 1.5 kcal/mol lower in energy than SOB. 

Alcohol No. OH groups Oxyalkylating agent Solvent Catalyst Reaction conditions Temp Pressure (°C) (psi) Ref. 

A polymer composite with a low glass transition temperature has been described as based on layered photoconductive polymers, namely, poly(p-phenylene terephthalate carbazole)s. " These polymers consist of a rigid backbone of poly(pentylene terephthalate) with pendant oxyalkyl carbazole groups. When the host polymers are mixed with various dopants, the layers are preserved and their layer distance increases, indicating that all the guest molecules are confined to the nanoscale interlayer space. 

On the other hand, oxyalkyl-substituted polymers are also potentially attractive for the known cation coordinating properties of their ether groups, which are expected to improve ionic transport in the polymers and, hence, to give faster electrochromic response time. The ether-group compatibility of these polymers with polyethylenoxide-based polymer electrolytes is also expected to improve the electrode-electrolyte contact in solid-state electrochromic devices. 

Several additional homo-, co-, and terpolymers based on P3ATs have been synthesized recently. Monomers that incorporate two or three thiophenes such as the 4,4-dialkyl-2,2 -bithiophenes or 3,3-dialkyl-2,2 -bithiophenes with various substituent groups such as alkyl, oxyalkyl, )3-aryl have been prepared by chemical and electrochemical methods (134-137). 

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