Polyethylene glycol compound preparation

Finally, the 1,3-dione systems prepared by Cram and Alberts deserve special note . These compounds, referred to as hexahosts are similar to the polymer-bound material illustrated as Compound 29 in Chap. 6. The synthesis is based on a methylene-bridged bis-dithiane unit. One of these may be cyclized with a polyethylene glycol, or more than one unit may be incorporated to give multiple 1,3-dione binding sites in the macrocycle. The former case is illustrated in Eq. (3.46). 

With the discovery of the crowns and related species, it was inevitable that a search would begin for simpler and simpler relatives which might be useful in similar applications. Perhaps these compounds would be easier and more economical to prepare and ultimately, of course, better in one respect or another than the molecules which inspired the research. In particular, the collateral developments of crown ether chemistry and phase transfer catalysis fostered an interest in utilizing the readily available polyethylene glycol mono- or dimethyl ethers as catalysts for such reactions. Although there is considerable literature in this area, much of it relates to the use of simple polyethylene glycols in phase transfer processes. Since our main concern in this monograph is with novel structures, we will discuss these simple examples further only briefly, below. 

The materials shown and described above were generally prepared from the nucleophilic phenoxide or alkoxide and the appropriate bromide. The syntheses of a variety of such compounds were detailed in a report which appeared in 1977. In the same report, complex stability and complexation kinetics are reported. Other, detailed studies, of a similar nature have recently appeared" . Vogtle and his collaborators have also demonstrated that solid complexes can be formed even from simple polyethylene glycol ethers . Crystal structures of such species are also available... 

Lipase has been used in organic solvents to produce useful compounds. For example, Zark and Klibanov (8) reported wide applications of enzymes to esterification in preparing optically active alcohols and acids. Inada et al (9) synthesized polyethylene glycol-modified lipase, which was soluble in organic solvent and active for ester formation. These data reveal that lipases are very useful enzymes for the catalysis different types of reactions with rather wide substrate specificities. In this study, it was found that moditied lipase could also synthesize esters and various lipids in organic solvents. Chemically moditied lipases can help to solve today s problems in esteritication and hopefully make broader use of enzymatic reactions that are attractive to the industry. 

A 20% polyethylene glycol succinate on Kieselguhr column (1.2 m, 443 K, 50 ml min helium carrier gas) was used for GC analyses. Deuterium-labelled compounds were analysed by NMR spectroscopy (JEOL C 60-HL equipment) after separation with a Carlo Erba Mod P preparative GC. Mass spectrometric analyses of the reaction mixtures were carried out with a Hewlett Packard 5890A GC instrument (25 m HP-20M column, 353-473 K) coupled with a 5970 MSD quadrupole mass spectrometer (El source, 70 eV, 1-s scans, HP 59970 MS ChemStation data system). 

Sets A and C were applied as mixtures prepared from equal weight parts of each of the contaminants. In sets B and D, the mixtures had to be diluted in a ratio 1 5 with polyethylene glycol 400 (PEG 400). This was done to reduce vapour pressure and the agressiveness of set B and D compounds, because these compounds are sorbed to a relatively high degree into the PET matrix thus swelling the material. 

Carbenes, generated by photolysis of di- and tetrachloro-o-quinone diazides, react with oxetane in a 1 3 ratio to afford 15-membered crown ethers. Benzocrown ether 675 was obtained in 16% yield (91CB1865). Derivatives of macrocyclic crown ethers with four or five oxygen atoms in a ring were synthesized by Cu(acac)2-catalyzed cyclization of a,polyethylene glycols. 20-26-Membered crown-4(5) ethers 676 were prepared from the above-mentioned diazo ketones with tri- or tetra-ethylene glycols in 7-26% yields. Treatment of l,8-bis(diazoacetyl)octane with dodecane-l,12-diol under the same conditions results in a mixture of 52-membered tetraether 646 (40%) and compound 645 (81CC616). 

---