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