{HEAD ~ The compound} 2 wherein R4 is {TAIL ~ an substituted or unsubstituted phenyl or thienyl group} 
{ HEAD ~ The compound } 2 wherein R4 is { TAIL ~ an substituted or unsubstituted phenyl or thienyl group }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL