Glycol boronates, cyclic

Cyclic glycol boronates from glycols and lithium hydridotrialkylborates... 

Osmium tetroxidejN-methylmorpholine N-oxide Cyclic glycol boronates from ethylene derivs. 

Kawakami, Suzuki and Yamashita showed that compound 7, among many others, could be polymerized to derivatives of the corresponding open-chained species by treatment with boron trifluoride ether complex. Yamashita and Kawakami formed these same sorts of materials by heating the glycols and paraformaldehyde in the presence of toluenesulfonic acid. This led to prepolymers which were then thermally depolymerized to afford the cyclic oligomers which were separated by fractional distillation. 

Elimination of Water. Effect of benzeneboronic anhydride is shown by Reactions 3, 4, and 5. The reaction products, cyclic ethylenebenzene-boronate and water, diffused more readily through the PET polycondensation system than did ethylene glycol. 

Prominent among copolymers of cyclic ethers are interpolymers of oxiranes with tetrahydro-furan. Thus, ethylene oxide copolymerizes with tetrahydrofuran with the aid of a boron trifluoride-ethylene glycol catalytic system. The resultant copolyether diol contains virtually no unsaturation. 

A characteristic chemical feature of boronic acids is the formation of reversible covalent complexes with 1,2- or 1,3-diols such as ethylene glycoL sugars, and polysaccharides. In aqueous solutions, boronic adds exist in equilibrium between an undissociated neutral trigonal form and a dissociated anionic tetrahedral form. In the presence of diols, neutral boronic acids barely form cyclic boronale esters by reaction with diols because these esters are generally hydrolytically unstable, but boronate anions form stable anionic boronate esters. Thus, the formation of complexes depends on the pH of the solution and pK of the boronic acid. 

Cyclic formats of 1,3-glycols are prepared by patented proces.ses involA -ing the reactions of olefins A i,th formaidehyde in the presence of acidic catalA-sts,. such as boron fluoride, mineral acids, zinc chloride,... 

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