25691
The unusual intramolecular arene / allene cycloaddition described 30 years ago by Himbert permits rapid access to strained polycyclic compounds that offer great potential for the synthesis of complex scaffolds .
 Chemical: arene; Chemical: allene
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: arene; Chemical: allene