Synthesis and polymerization of racemic and optically active β-monosubstituted β-propiolactones

Abstract

The reaction of ketene with chloral and 2,2-dichloropropanal leads, respectively, to the synthesis of 0-(trichloromethyl)-0-propioIactone (CC13-PL) and ß-(1,1-dichloroethyl)-0-propiolactone (CH3CC12-PL). Both monomers were prepared in the optically active form with enantiomeric excesses of 100% and 95% for CCI3-PL and CH3CC12-PL, respectively, using quinidine as a catalyst, and an enantiomeric excess of 100% for CH3CC12-PL using brucine as a catalyst. Both monomers were also prepared in the racemic form. Enantiomeric excesses were determined from optical rotation (CC13-PL) or NMR spectroscopy (CH3CC12-PL and CC13-PL) after complexation of the lactone with a europium chiral shift reagent. Polymerization was carried out in bulk and toluene solution, under vacuum, using mainly triethylaluminum as initiator. Solution characterization of the polymers was conducted by viscometry, osmometry, and gel permeation chromatography. The polymers prepared from optically active monomers are less soluble in organic solvents than those prepared from racemic monomers.In addition, the former polymers are crystalline and exhibit a high-temperature melting peak (Tm = 275 °C for poly(CCl3-PL) and 235 °C for poly(CH3CC12-PL)) whereas the latter polymers are amorphous and decompose at about 200 °C.

Functional biodegradable polymers via ring-opening polymerization of monomers without protective groups

“…cycloaddition from ketene and the corresponding mono-, di-or trichlorinated acetaldehyde and intensively investigated in their polymerization behavior and tacticity of obtained polymers (Schemes 7, 1A). Prud'Homme and coworkers further introduced several chlorinated and fluorinated propiolactones (A32-A36), [97][98][99] partially being b-disubstituted at the lactone ring (Scheme 7, 1A-3A). For racemic mixtures of the monomers, they used the corresponding halogenated aldehyde (or halogenated acetone or butanone for b-di substituted lactones), acetyl chloride and triethylamine, for optically active monomers they used the synthetic route using ketene and the chiral catalyst quinidine.…”

Total Synthesis of Biselide A, A Cytotoxic Macrolide of Marine Origin

“…10,11 Preparation of dichloroolefin 33 was carried out based on a procedure reported by Roulland 4 and Cossy 8b with modification (Scheme 4). Thus, reduction of racemic β-(trichloromethyl)-β-propiolactone (35), 12 which was prepared from chloral, gave diol 36. The primary hydroxy group in 36 was selectively protected by a TBS group, and acetylation of the secondary hydroxy group gave acetate 37 by a one-pot procedure.…”

Synthesis and Characterization of Racemic and Isotactic Poly(β-alkyl-β-propiolactone)s

“…Synthesis of Racemic β -(Trichloromethyl)- β -propiolactone (CCl 3 - PL). The synthesis of racemic β-(trichloromethyl)-β-propiolactone (CCl 3 -PL) was carried out from chloral and acid chloride (eq 1) according to the method described by Lavallée et al, without further modification (yield: 89%):

…”

“…Synthesis of Racemic β -(Dichloroethyl)- β -propiolactone (CH 3 CCl 2 - PL). The synthesis of racemic β-(dichloroethyl)-β-propiolactone (CH 3 CCl 2 -PL) was carried out from 2,2-dichloropropanal and ketene, following eq 3, according to the method described by Knunyants and Cherbukov (yield: 63%): The synthesis of optically active CCl 3 -PL, CH 3 CCl 2 -PL, and C 2 H 5 CCl 2 -PL was carried out according to the method described by Prud'homme and co-workers, , without further modification. The addition of an optically active catalyst, like quinidine, to the reaction medium allows the obtention of β-(chloroalkyl)-β-propiolactones with the ( R ) stereochemical configuration and a high optical purity.…”

“…Optically active β-PL can also be prepared by a method initially described by Wynberg and Staring , that involves a reaction between ketene and aldehydes in the presence of a chiral base, as quinidine and quinine. This method was used with success in our laboratory, to prepare, for instance, β-(trichloromethyl)-, β-(dichloroethyl)- and β-(dichloropropyl)-β-propiolactone (CCl 3 -PL, CH 3 CCl 2 -PL, and C 2 H 5 CCl 2 -PL, respectively) with a 100% enantiomeric excess and very good yields. − These monomers were then polymerized, using mainly ZnEt 2 /H 2 O 39 or AlEt 3 /H 2 O 38 as catalysts; crystalline and highly isotactic polymers were obtained, indicating that little or no racemization occurred in the course of the polymerization.…”