Polyethylene glycol reduction reactions

Gas chromatographic analyses are obtained at about 120° with a 2 m. X 7 mm. column packed with a suspension of 5% (by weight) of silver nitrate and 15% (by weight) of Carbowax 6000 (polyethylene glycol) on either Chromosorb P or Celite 545. With this column the relative retention times of the various possible components in the reaction mixture are cyclododecane, 1.00 trans,trans,trans-, S,9-cyc ododec tnene, 1.20 trans-cyclo-dodecene, 1.13 m-cyclododecene, 1.33 ci5,iraw5-l,5-cyclodode-cadiene, 1.51 m, m 5-/raw5-l,5,9-cyclododecatriene, 1.72. The reaction should be stopped when the rate of reduction of cis,trans-1,5-cyclododecadiene to cw-cyclododecene has become approximately equal to the rate of conversion of the as-monoolefin to cyclododecane. 

A sodium hydroxide/polyethylene glycol system was used in the reductive decya-nation of diphenylacetonitriles to give diphenylmethanes in high yield. Thermal reaction times of 60 min could be reduced to 2 min under microwave irradiation (Scheme 4.43)69. 

The advantages of PTC reactions are moderate reaction conditions, practically no formation of by-products, a simple work-up procedure (the organic product is exclusively found in the organic phase), and the use of inexpensive solvents without a need for anhydrous reaction conditions. PTC reactions have been widely adopted, including in industrial processes, for substitution, displacement, condensation, oxidation and reduction, as well as polymerization reactions. The application of chiral ammonium salts such as A-(9-anthracenylmethyl)cinchonium and -cinchonidinium salts as PT catalysts even allows enantioselective alkylation reactions with ee values up to 80-90% see reference [883] for a review. Crown ethers, cryptands, and polyethylene glycol (PEG) dialkyl ethers have also been used as PT catalysts, particularly for solid-liquid PTC reactions cf. Eqs. (5-127) to (5-130) in Section 5.5.4. 

Phthalimide-N-sulfenyl chloride, 375 Phthaloylamino acids, 212 Phthaloyl-L-valine, 212 Phytuberin, 197 Phytyl chloride, 499, 500 Picrotoxinin, 265, 430 Pictei-Spengler cyclization, 308 Pinacol-typc reduction, 513 -Pinene, 346, 367 Piperidine acetate, 318 Piperidinium acetate, 375-376 Polonovski reaction, 484 Polyaminolactams, 378-379 Polycyclic phenols, 102 Polyene cyclization, 291-292 Polyethylene glycols, 360, 376 Polyketides, 302 Polyphosphate ester, 376-377 Polyprenylation, 499-500 Potassium-Ammonia, 273, 377 Potassium-t-Butylamine-18-Crown-6, 377-378... 

Liquid polyethylene glycol in organic synthesis. Three main types of reaction have been studied substitution, oxidation and reduction (Figure 8.5). The Diels Alder reaction is frequently used as a benchmark for alternative reaction media. For the reaction of 2,3-dimethyl-1,3-butadiene with nitrosobenzene in PEG 300 or PPG 425, a 3.3-fold increase in rate was seen compared with dichloromethane and a 2.5-fold increase compared with ethanol. It has also been shown more recently that in comparison to conventional solvents, the transition state for the Diels-Alder reaction is stabilized in aqueous PEG solutions and this results in a lower activation energy. ... 

Method H is closely related to the previous method since it is catalysed by Pd-C, however, with zinc as terminal reductant. The reactions have been performed in water / acetone (1 1) mixture [61], or water [62,63] as the only reaction solvent. In the latter case, the addition of a nonionic surfactant, polyethylene glycol (PEG-400) [62] or 18-crown-6 [63] was essential to obtain high conversions and high yields of homo-coupled products. The PEG and crown ethers probably provide water-soluble forms of aryl halides, otherwise almost water-insoluble materials. The method is efficient in the homo-couplings of all types of aryl halides, including chlorides at elevated temperatures [62]. 

Under the assumption of bimolecular termination, the reaction diffusion parameter R (equation (4.2)) was determined for the bulk photopolymerization of multifunctional (meth)acrylates [I, 3, 6, 17, 481. It was found that for methacrylates at the plateau level, R was in the order of 2 1 moP [6] and for acrylates R was 3-5 1 moP [I7J. In general, reduction of network cross-linking density by co-polymerization with a difunctional reactive diluent (2-hydroxyethyl methacrylate (HEMA), octyl methacrylate) [3] increased the values of R due to increased mobility of the polymerization system until a plateau is reached. The addition of an inert diluent (polyethylene glycol 400 (PEG 400) [3, 6] or hydrogenated monomers [25. 53]) to a flexible monomer of low viscosity did not change R,... 

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