Fucoidan-mediated green synthesis of palladium nanoparticles as a recyclable catalyst for Heck coupling and alkyne reduction in pheromone synthesis.

The development of sustainable routes for metallic nanocatalysts remains challenging due to the reliance on toxic reagents and harsh synthesis conditions. To address this, a green and efficient method was established for the preparation of palladium nanoparticles (PdNPs@Fu) using fucoidan, a naturally occurring polysaccharide with several hydroxyl and sulfate groups as a stabilizing and reducing agent. Fucoidan can rapidly reduce Pd2+ to Pd0 in aqueous medium under microwave irradiation (450 W, 10 min). The resulting PdNPs@Fu exhibited uniform crystalline nanoparticles (sizes ranging from 2-6 nm and an average diameter of 3.83 ± 0.09 nm), with long-term colloidal stability over 30 days. Catalytic studies demonstrated remarkable activity in model organic transformations: the Heck coupling (93% yield, 84% after five cycles) and the selective semi-hydrogenation of alkynes to (Z)-alkenes (94% yield, 85% retained activity). Notably, the catalyst afforded an overall yield of 78% in the synthesis of the sweet potato weevil (Cylas formicarius) pheromone. This research introduces a green synthesis strategy of PdNPs, integrating nanotechnology with efficient pheromone synthesis for insect control.