Hidroaminometilação do -pineno e do estragol catalisada por complexos de ródio(I) promovidos por ligantes de fósforo

Abstract

Amines are important building blocks in the synthesis of pharmaceuticals, agrochemicals, surfactants and other fine chemicals. However, these compounds are industrially synthesized through inefficient reactions that make use of toxic and hazardous chemicals, generating a substantial amount of waste. Hydroaminomethylation is an environmentally benign tandem catalytic process comprised of three consecutive reactions: hydroformylation of an alkene, aminecondensation and hydrogenation of the formed enamine. This reaction is well suited for green chemistry, making possible the synthesis of structurally complex amines from cheap and renewable substrates.The rhodium-catalyzed hydroaminomethylation of the renewable substrates -pinene and estragole was extensively studied by optimization of the main reaction parameters: catalytic precursor/ligand ratio, temperature, solvent, ligand structure, amount of catalyst, addition of acid co-catalysts and the amine counterpart. The hydroaminomethylation of b-pinene was carried out in ethanol in the presence of thebulky phosphite P(O-o-tBuPh)3 as ligand with 81% selectivity for amines, the best result reported until the present time. Furthermore, new amines derived from -pinene with potential biological activity were synthesized in one step using this reaction. Over 99% of selectivity to amines was reached in the hydroaminomethylation of estragole when the phosphite P(O-o-tBuPh)3 was used as ligand in ethanol, and over 80% when TPPTS was used as ligand in water. The functionalization of the substrates also happened smoothly in other environmentally benign solvents such as diethylcarbonate, 2-methyltetrahydrofuran,p-cymene and water, reassuring hydroaminomethylation as an economic and sustainable alternative for the synthesis of amines.