Dichlorocarbene adducts of 1,4-Polybutadienes. Improved synthesis and characterization by high-field NMR.

An improved method for obtaining the dichlorocarbene adducts of 1,4-polybutadienes is described. The procedure involves mild, nonbasic and homogeneous reaction conditions to generate dichlorocarbene from the organomercury precursor phenyl(bromodichloromethyl) mercury in the presence of polybutadienes. This methodology represents a significant improvement over treatment of chloroform with strong base in that strictly neutral conditions are employed; no block structure results and high degrees of conversion can be achieved readily. Thus complete double bond conversion provides the structural equivalent of 1:1 poly (dichlorocyclopropene- co-ethylene) with configurational control at the cyclopropyl ring. We use high-field NMR to characterize the chemical microstructures of the adducts from both cis- and trans-1, 4-polybutadienes at varying extents of cyclopropanation.