Helical Materials with Chiral Mo(II) Catalysts

Abstract

Helical mesoporous materials of the MCM-41 type with two different pore sizes were prepared by one-pot synthesis procedure using myristyl (C14) or cetyl (C16) trimethyl ammonium salts as templates. They were functionalized with the MoI2(CO)3 fragment, using a 2-aminopyridine glycidyloxypropyl derivative as anchoring ligand. TEM images showed the helical nature of the material channels. The new materials were tested as catalytic precursors in the epoxidation of cis-cyclooctene, styrene, cis-3-hexen-1-ol, trans-2-hexen-1-ol, geraniol, and R-(+)limonene, using tert-butylhydroperoxide as oxidant, and were in general moderately to highly selective towards the epoxide products. The catalytic activity of materials is higher than that of the corresponding homogeneous catalyst for epoxidation of cis-cyclooctene and styrene. The major achievement of these two catalysts, however, is the excellent product selectivity control, which in both cases reaches 100 % of the 2S,3R diastereomer in the epoxidation of trans-hex-2-en-1-ol. The catalysts were also found to be truly heterogeneous with no leaching, and stable through recycling experiments, despite losing some activity.