Mesoporous molecular sieve Sn-MCM-41 as Baeyer-Villiger oxidation catalyst for sterically demanding aromatic and α,β-unsaturated aldehydes

Sn-Beta is a successful Baeyer-Villiger oxidation catalyst for hydrogen peroxide, with a regular pore system with a 0.6 to 0.7 nm diameter. Diffusion of sterically more demanding substrates may be impeded, and therefore the mesoporous molecular sieve Sn-MCM-41 ( channel diameter of 3.5 nm) is reported here as an alternative catalyst for several substrates involving cyclocitral ( 6), safranal ( 10), myrtenal ( 14), cinnamaldehyde ( 18, X = H), para-methoxycinnamaldehyde ( 18, R = OMe) and piperonal ( 22). The oxidation system Sn-MCM-41/hydrogen peroxide provides the Baeyer-Villiger oxidation product of all these alpha,beta-unsaturated- or aromatic aldehydes with excellent selectivities and conversions up to 90%. Furthermore, except for cinnamaldehyde, the Sn-MCM-41 provides higher conversions than Sn-Beta - that can be attributed to the larger pore diameter and less to impediments to diffusion.