+ + + + +

Acetaldehyde, formaldehyde and ammonia react together in the gas phase to produce a mixture of pyridine and 3-picoline. The product ratio can be altered by changing the ratio of fee aldehydes.

Industrial Organic Chemistry, 3rd. Ed. K. Weissermel, H.-J. Arpe, VCH (1997)

Reaction defined as:
Condensation
Cyclisation
Industrial Process: Organic