Miscellaneous Oxygen Heterocyclics

Spiroorthocarbonates and spiroorthoesters are stable toward bases and nucleophiles but easily undergo cationic ROP. Cationic ROP of a spiroorthocarbonate (LXX) proceeds by initial formation of carbocation LXXI in which the carbocation center is stabilized by 

Takata and Endo, 1988]. A cyclic carbonate and cyclic ether are eliminated as by-products in reaction pathways a and b, respectively. Polymer LXXIV contains both ether and carbonate functional groups in the polymer chain. 

Various spiroorthoesters also undergo cationic polymerization, for example, 1,4,6-triox-aspiro[4.4]nonane (LXXV) yields a polymer containing both ether and ester groups in the polymer chain [Bailey, 1975 Matyjaszewski, 1984 a,b]. 

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Miscellaneous Uses. Outside of the protective group arena, MEMCl has been used to alkylate enolates and aryllithium reagents in the presence of Ph2TlBr. MEM ethers have also proven to be a good one-carbon source for the preparation of isochromans (eq 5) and other oxygen heterocycles (eq 6). ... 

Meldrum s acid, 172 Tin(IV) chloride, 300 Containing two oxygens N-Bromosuccinimide, 49 Other six-membered heterocycles Diethoxytriphenylphosphorane, 109 Miscellaneous heterocycles of any ring size... 

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