Nano n-propylsulfonated gamma-Fe2O3 as a new sulfonated nanomagnetic iron oxide was synthesized directly through ring opening reaction of 1,3-propanesultone with nano magnetic gamma-Fe2O3 and used as magnetically recyclable heterogeneous catalyst for the efficient one-pot synthesis of beta-phosphonomalonates. The catalyst was easily isolated from the reaction mixture by magnetic decantation using an external magnet and reused at least five times without significant degradation in the activity. (C) 2011 Elsevier B.V. All rights reserved.