The present invention relates to a polymer obtained from the polymerization of: (i) at least one monomer of formula (I) (CH
2
═CR
1
)CO—K (1) wherein: K represents O—Z or NH—Z, Z representing (CR
2
R
3
)m-CH
3
, (CH
2
—CH
2
—O)m-H, (CH
2
—CH
2
—O)m-CH
3
, (CH
2
)m-NR
4
R
5
with m representing an integer from 1 to 30; R
1
, R
2
, R
3
, R
4
and R
5
independently represent H or a C1-C6 alkyl; (ii) at least between 0.1 and 50% mol, advantageously between 1 and 30% mol, more advantageously between 1 and 20 mol % of a cyclic monomer having a exomethylene group of formula (II) wherein: R6, R7, R8 and R9 represent independently H or a C5-C7 aryl group or R6 and R9 are absent and R7 and R8 form together with the carbon atom on which they are bonded a C5-C7 aryl group; i and j represent independently an integer chosen between 0 and 2; X represents either O or X is not present and in this latter case, CR6R7 and CR8R9 are linked via a single bond C—C and (iii) at least one bio-resorbable block copolymer cross-linker.
Preparation of Racemic and Enantiomerically Pure Cyclic Ketene Acetals
作者:A. Díaz-Ortiz、E. Díez-Barra、A. de la Hoz、P. Prieto
DOI:10.1080/00397919308009850
日期:1993.7
Abstract Cyclic keteneacetals have been prepared from a-haloaldehyde dimethylacetals by transacetalization and subsequent elimination in PTC without solvent conditions. No racemization has been observed when an enantiomerically pure diol has been used. Stability and storage conditions have been studied.
A new methodology leading to ketene O,O- and S,S-acetals is reported. The title compounds were prepared from the corresponding halogenated precursors under microwave irradiation in the absence of solvent within 5–25 minutes with excellent yields. Yields obtained under microwaves are by far the best when compared to those obtained by ultrasound or classical heating in the same conditions of time and