iels – A lder ▁re actions ▁with ▁electron - def ic ient ▁di en oph iles ▁such ▁as ▁eth yl ▁( E )- 3 - nit ro ac ry late . ▁The ▁reaction ▁product ▁is ▁a ▁mixture ▁of ▁is om ers ▁with ▁preference ▁for ▁the ▁end o ▁is omer : ▁ ▁D iels - A lder ▁reaction ▁of ▁fur an ▁with ▁ar yn es ▁provides ▁corresponding ▁derivatives ▁of ▁di h yd ron aph th alen es , ▁which ▁are ▁useful ▁inter medi ates ▁in ▁synth esis ▁of ▁other ▁poly cyc lic ▁a rom atic ▁comp ounds . ▁▁ ▁H ydro gen ation ▁of ▁fur ans ▁sequ entially ▁aff ords ▁di h ydro fur ans ▁and ▁t et rah ydro fur ans . ▁ ▁In ▁the ▁Ach mat ow icz ▁reaction , ▁fur ans ▁are ▁converted ▁to ▁di h yd ropy ran ▁comp ounds . ▁ ▁P yr role ▁can ▁be ▁prepared ▁industri ally ▁by ▁react ing ▁fur an ▁and ▁am mon ia ▁in ▁the ▁presence ▁of ▁solid ▁acid ▁catal yst s , ▁such ▁as ▁Si O 2 ▁and ▁Al 2 O 3 . ▁ ▁Saf ety ▁Fur an ▁is ▁found ▁in ▁heat - tre ated ▁commercial ▁food s ▁and ▁is ▁produced ▁through ▁thermal ▁de grad ation ▁of ▁natural ▁food ▁constitu ents . ▁It ▁can ▁be ▁found ▁in ▁ro asted ▁coffee , ▁instant ▁coffee , ▁and ▁processed ▁baby ▁food s . ▁Research ▁has ▁indicated ▁that ▁coffee ▁made ▁in ▁es press o ▁mak ers , ▁and , ▁above ▁all , ▁coffee ▁made ▁from ▁caps ules