1,5 Dioxepan-2-one

These representative aliphatic polyesters are often used in copolymerized form in various combinations, for example, poly(lactide-co-glycolide) (PLGA) [66-68] and poly(lactide-co-caprolactone) [69-73], to improve degradation rates, mechanical properties, processability, and solubility by reducing crystallinity. Other monomers such as 1,4-dioxepan-5-one (DXO) [74—76], 1,4-dioxane-2-one [77], and trimethylene carbonate (TMC) [28] (Fig. 2) have also been used as comonomers to improve the hydrophobicity of the aliphatic polyesters as well as their degradability and mechanical properties. 

The 2,3-dihydro-5//- l, 4-dioxepins (363) and (365) can be obtained from 1,4-dioxin-halocarbene adducts (364) (77ZC331). Saturated rings of type (366) have been prepared by the treatment of cyclic acetals of ethane-1,2-diol with vinyl ethers in the presence of boron trifluoride. 1,4-Dioxepan-5-one (367) results from the reaction of bromoform and silver nitrate with aqueous dioxane (60AG415). 

The noncatalytic oxidation of 4,7-dihydro-l,3-dioxepin 46a with nitrous oxide in liquid phase at 220 °C produces 1,3-dioxepan-5-one however, the conversion is very slow <2004ASC268>. 

Mulzer et al. have extended the applicability of the insertion reaction of ketene into an acetal, to that of a substituted ketene into a 1,3-dioxalane to provide an elegant synthesis of 6,6-dichloro-l,4-dioxepan-5-ones (Equation 13) <1996AGE1970>. 

Dioxepan-2-ones (103) have been manufactured from diols, paraformaldehyde, and carbon monoxide in the presence of a copper(I) or silver carbonyl catalyst (Scheme 10). Thus, treatment of CU2O with 98% H2SO4 and CO and reaction with paraformaldehyde and 1,2-propanediol under CO atmosphere gave 5-methyl-l,4-dioxepan-2-one in high yield <89JAP0i09358i>. By the same protocol, l,4-dioxepan-2-one could be obtained by cyclocondensation of trioxane with CO and... 

The monomers that have been used for the synthesis include glycolide, lactide, (3-propiolactone, (3-butyro lactone, y-butyrolactone, 6-valerolactone, e-caprol-actone, l,5-dioxepan-2-one, pivalolactone, l,4-dioxane-2-one, 2-methylene-1, 3-dioxolane, 2-methylene-l, 3-dioxepane, etc. The structures of some of these monomers are given in Table 1. 

Dioxane 1,4-Dioxane-2,5-dione 1,4-Dioxane-2,6-dione Dioxathion 1,3-Dioxepane 1,3-Dioxolane 1,3-Dioxol-2-one Dioxybenzone... 

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