Egon Spengler It is implied in one episode of the animated series that Spengler accidentally burned down his family's garage. Spengler is the only original Ghostbuster to return for the "Extreme Ghostbusters" series as a regular, acting as a mentor to the new Ghostbusters (the others appeared for a two-part episode, "Back in the Saddle"), and monitoring and sustaining the Containment Unit while working as a paranormal studies professor at a university. He is the de facto leader of the new, younger team of Ghostbusters; although the old team had gone into retirement after they apparently dealt with all the ghosts in
Pictet–Spengler reaction tetrahydroisoquinoline synthesis. Reaction conditions are generally harsher than the indole variant, and require refluxing conditions with strong acids like hydrochloric acid, trifluoroacetic acid or superacids. Instead of catalyzing the Pictet-Spengler cyclization with strong acid, one can acylate the iminium ion forming the intermediate "N"-acyliminium ion. The "N"-acyliminium ion is a very powerful electrophile and most aromatic ring systems will cyclize under mild conditions with good yields. Tadalafil is synthesized via the "N"-acyliminium Pictet–Spengler reaction. This reaction can also be catalyzed by AuCl and AgOTf. When the Pictet–Spengler reaction is performed with an aldehyde other than formaldehyde, a new chiral center