22710
The latter were refluxed with substituted secondary amines and formaldehyde for 6 - 10 h to afford Mannich bases ( 5a - k ) .
 Chemical: secondary amines; Chemical: formaldehyde; Chemical: Mannich bases
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: secondary amines; Chemical: formaldehyde; Chemical: Mannich bases