1. Dominant Industrial Route (Ethyl Acetate Route, over 95% global capacity)

This mature process relies on triazinamide (P4) as the exclusive core intermediate for building the triazinone parent ring.

1. Ethyl acetate reacts with hydrazine hydrate via hydrazinolysis to form acetohydrazide.
2. Acetohydrazide cyclizes with phosgene to produce methyloxadiazolone.
3. Alkylation with chloroacetone yields acetonyloxadiazolone.
4. Further hydrazinolysis with hydrazine hydrate generates triazinamide (CAS:136738-23-3) with high purity.
5. Acid hydrolysis removes the acetyl group of triazinamide to obtain aminotriazinone.
6. Final condensation with nicotinaldehyde (3-pyridinecarboxaldehyde) affords crude pymetrozine, then refined to technical grade.

Features: Low-cost raw materials, stable operation, total yield 50%–55%; triazinamide is irreplaceable in mass production.

2. Obsolete Trifluoroethyl Acetate Route

It also forms triazine intermediates but uses expensive trifluorinated feedstocks, discharges massive wastewater, and suffers poor economy. This route has been fully phased out commercially.

3. New Green Carbazide Route (Lab & Pilot Scale Only)

A patented three/four-step eco-friendly pathway without triazinamide intermediate:

1. Dimethyl carbonate reacts with hydrazine hydrate to synthesize carbohydrazide.
2. Condensation between carbohydrazide and nicotinaldehyde forms pyridinylmethylene carbohydrazide.
3. Cyclization with chloroacetone directly constructs pymetrozine skeleton.

Drawbacks: Low cyclization selectivity, many impurities, total yield below 40%; no large-scale industrial application yet.

4. Nicotinaldehyde Preparation Sub-path

• Mainstream: 3-cyanopyridine hydrogenation produces nicotinaldehyde, high yield (~90%) for condensation.
• Schiff base route: Higher catalyst cost, rarely adopted in factories.