2-oxabicyclo octane, polymerization

The conformation and the ring strain involved in bicyclo [3.3.0] octanes has been discussed by Armarego102). The cis-fused isomers are more stable than the trans ones. Therefore, trans-3-oxabicyclo [3.3.0] octane polymerizes but ds does not30). 

The addition of ZnBi 2 to die tandem 1,3-azaprotio cyclotransfer-cycloaddition of a ketoxime with divinyl ketone results in rate enhancement and the exclusive formation of l-aza-7-oxabicyclo[3.2.1]octan-3-ones.79 The 1,3-dipolar cycloaddition of 1-aza-l-cyclooctene 1-oxide with alkenes produces the corresponding isoxazolidines in high yields with a minimum of polymeric material.80 The cycloaddition of thiophene-2 -carbaldehyde oxime with acetonitrile and methyl acrylate produces the 1,3-dipolar adduct, substituted isoxazolidines, and not the previously reported 4 + 2-adducts.81 Density functional theory and semi-empirical methods have been used to investigate the 3 + 2-cycloaddition of azoxides with alkenes to produce 1,2,3-oxadiazolidines.82 The 3 + 2-cycloaddition of a-nitrosostyrenes (62) with 1,3-diazabuta-l,3-dienes (63) and imines produces functionalized cyclic nitrones (64) regioselectively (Scheme 22).83... 

As mentioned before, the AHg, value for the polymerization of 6,8-dioxabicyclo [3.2.1] octane is less negative than that for l,3-dioxolanes. Bicyclo [3.2.1] octane, in which a five-membered ring is fused to a cyclohexane ring at two axial positions, has 51 kJ/mol strain energy. However, from the fact that 7-oxabicyclo [2.2.1] heptane has less strain energy than bicyclo [2.2.1] heptane can be deduced that the strain energy of 6,8-dioxabicydo [3.2.1] octane may also be less than that of bicyclo [3.2.1] octane. 

Another type of bJock-copolymer was obtained by conversion of living ROMP into controlled atom-transfer radical polymerization (ATRP). The approach involves the termination of a living ROMP polymer with a />bromomethylbenzaldehyde. This prepolymer may be Initiated using CuBr/2,2-dipyridyl and used for bJock-copolymer formation with styrene and methyl acrylate (Scheme 48). Finally, the preparation of 7-oxabicyclo[2.2.1]hept-2-ene-5,6-dimetha-nol-derived ROMP polymers and their use for the preparation of 7V-alkyl-3-aza-8-oxabicyclo[3.2.1]octane-... 

Finally the preparation of polyesters by ring-opening polymerization of bicyclic lactones will briefly be mentioned. This type of polymerization has previously been investigated. However, it is only recently that the importance of controlling the stereochemistry has been demonstrated. In this study the polymers obtained from 2-oxabicyclo[2.2.2]octan-3" one (19) were characterized by NMR. 

Sumitomo and coworkers prepared 6,8-dioxabicyclo[3.2.l]octan-7-one (37) and 6-aza-8-oxabicyclo[3.2.lJoctan-7-one (36) from 3,4-dihydro-2H-pyran-2-carbaldehyde (acrolein dimer), and polymerized these monomers by ring-opening methods (Fig. 15). The lactam (36) was polymerized to a high molecular weight polyamide (39). 

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