N,N-Dimethylbiguanide immobilized on mesoporous and magnetically separable silica: Highly selective and feasible organocatalyst for synthesis of β-nitroalcohols

An organosuperbase (N,N-dimethylbiguanide) immobilized on mesoporous and magnetically separable silica supports, was found for the first time, to act as a highly-stable, scalable and efficient heterogeneous catalyst for the Henry reaction under mild and neutral condition. Several factors such as catalyst amount, solvent and reaction time concerning the reactivity were also discussed. The procedure constitutes the first immobilized biguanide promotion of selective synthesis of β-nitroalcohols without addition of stoichiometric amount of any base and showed a broad substrate scope. The uniqueness of this catalyst lay in its cleanness, cost-effectiveness, ease in removal at the end of reaction, and chemoselective formation of a wide range of β-nitroalcohols. These materials can be easily converted to other useful synthetic intermediates which many of them have been exemplified in synthetic organic chemistry and pharmaceutical industry.