Ring strain oxetane

Compared to 1,4-butanediol, which forms tetrahydrofuran byproduct in PBT polymerization, PDO is difficult to cyclize into oxetane because of the high ring strain. Oxetane was not found in the byproduct analysis [23],... 

The four-membered oxetane ring (trimethylene oxide [503-30-0]) has much higher ring strain, and irreversible ring-opening polymerization can occur rapidly to form polyoxetane [25722-06-9] ... 

Because of the high ring strain of the four-membered ring, even substituted oxetanes polymerize readily, ia contrast to substituted tetrahydrofurans, which have tittle tendency to undergo ring-opening homopolymerization (5). 

The chemistry of polymerization of the oxetanes is much the same as for THE polymerization. The ring-opening polymerization of oxetanes is primarily accompHshed by cationic polymerization methods (283,313—318), but because of the added ring strain, other polymerization techniques, eg, iasertion polymerization (319), anionic polymerization (320), and free-radical ring-opening polymerization (321), have been successful with certain special oxetanes. 

Oxetane, 2-(o -chlorobenzyl)-2-phenyl-X-ray crystal structure, 7, 366 Oxetane, 3-chloromethyl-3-ethyl-ring strain, 7, 370-371 Oxetane, 2-(o-chlorophenyl)- H NMR, 7, 367 Oxetane, 2-cyano-synthesis, 7, 391-392 Oxetane, 2-cyano-3,3-dimethyl-2-phenyl-thermolysis, 7, 372 Oxetane, 2,2-dialkoxy-synthesis, 7, 396 Oxetane, 2,2-dialkyl-isomerization, 7, 377 Oxetane, 3,3-dialkyl-alkylative cleavage, 7, 381 polymers, 7, 382 Oxetane, 2-diethylamino-synthesis, 7, 390 Oxetane, 3,3-difluoro-molecular dimensions, 7, 365 Oxetane, 2,2-dimethyl-mass spectra, 7, 368-369 photolysis, 7, 373 synthesis, 7, 393 Oxetane, 2,3-dimethyl- H NMR, 7, 366 thermolysis, 7, 372 Oxetane, 2,4-dimethyl-mass spectrum, 7, 369... 

Oxetanes are significantly less reactive with nucleophiles due to diminished ring strain. Under certain conditions, however, amines can open oxetanes to give amino alcohols. tert-Butylamine reacts with oxetanes in the presence of Yb(OTf)3 to give 3-hydroxy amines. Lithium tetrafluorohorate has also been used for this... 

T. K. Wu The largest ring used so far was oxepane, but we are planning to go in the other direction, using four membered rings. However, in this case complications arise because the strained oxetane ring does not undergo equilibrium polymerization. 

The ring strain energies for 3,3-dimethyloxetane, 3,3-bis(chloromethyl)oxetane and 3-ethyl-3-chloromethyloxetane have been determined from the heats of formation and all have the same value of 93 kJ mol-1, showing a decrease in ring strain energy of 13.3 kJ mol-1... 

The ring-strain energy of oxetane is less than that of PO (106.7k] mol 1 versus llTZkJmoT1) hence, its copolymerization with C02 is less favored thermodynamically [3], Nevertheless, the copolymerization of oxetane and C02 occurs readily under similar catalytic conditions, producing poly(trimethylene carbonate),... 

Epoxides directly attached to the oxetane ring in l,5-dioxaspiro[3.2]hexanes (e.g., 71) can be ring-opened by certain nucleophiles without attack on the less-strained oxetane ring <19990L825, 2003JOC1480>. However, such reactions can alternatively lead to the formation of a-substituted-/3 -hydroxyketones. It was reported that the pAla of the nucleophile generally determines the reaction outcome (Scheme 13). 

In polymerizations of cyclic ethers with rings smaller than tetrahydrofuran, ring strain affects the position of the equilibria discussed above. Small cycles (oxiranes, oxetanes) cannot be formed from esters with ion pair formation, and the equilibrium is shifted in favour of the macroesters [33, 34],... 

Due to the high ring strain of 3- and 4-membered rings, oxiranes and oxetanes polymerize practically irreversibly. Thermodynamic polymeri-zability of these groups of monomers is not significantly affected by substi-... 

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