This in turn is then ring closed by a stereospecific process of {HEAD ~ inversion} with {TAIL ~ pyridine} in p toluenesulfonyl chloride to obtain dibenzofuran 
This in turn is then ring closed by a stereospecific process of { HEAD ~ inversion } with { TAIL ~ pyridine } in p toluenesulfonyl chloride to obtain dibenzofuran
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH