Synthesis and Radical Polymerization of Various 2‐Cyclopropylacrylates

Fourteen new alkyl 2‐cyclopropylacrylates 1a − n with various substituents R 1 −R 5 were synthesized from readily available precursors by applying standard transformations such as cyanohydrin formation from an aldehyde, alcoholysis to an α‐hydroxycarboxylic ester, oxidation and Wittig methylenation of an α‐oxocarboxylic ester. Overall yields ranged from 33 to 54%. A new method for the hydrolysis of dimethyl cyclopropanedicarboxylates to the corresponding half‐esters was developed. The α‐oxocarboxylates 7g − n were prepared by dirhodium tetraacetate catalyzed cyclopropanation of alkenes 8g − n with methyl or ethyl diazopyruvate in 32−58% yield. The monomers 1a − n were characterized by 1 H, 13 C NMR spectroscopy, mass spectrometry and elemental analysis. The radical homopolymerizations of 1a − n were carried out with 2,2′‐azabisisobutyronitrile (AIBN) as initiator in chlorobenzene at 65 °C. The highest polymer yields were obtained in the polymerizations of 1f and 1h or 1k and 1l , i.e. from monomers with an annelated five‐ or six‐membered ring. In the case of 1h and 1k , both the polymer yields (99 and 98%, respectively) and the glass transition temperatures ( T g ) of 57 and 93 °C were significantly higher than those observed for the polymer from 1,1‐bis(ethoxycarbonyl)‐2‐vinylcyclopropane ( DECVCP ), which was used as a benchmark for the monomer reactivities in the radical polymerizations of all the vinylcyclopropane derivatives 1a − n . The bicyclic monomers 1h and 1k also demonstrated drastically improved reactivities in the radical copolymerization with methyl methacrylate when compared to DECVCP . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)