OMS-2 for aerobic, catalytic, one-pot alcohol oxidation-wittig reactions: Efficient access to α,β-unsaturated esters

Article abstract of DOI:10.1002/cctc.201300942

Manganese oxide octahedral molecular sieve (OMS) materials with well-defined pores have been extensively studied over two decades due to their intriguing chemical and physical properties. OMS-2, the synthetic cryptomelane form of manganese oxide, was synthesized by a modified reflux method and was found to be highly active for obtaining α,β-unsaturated esters (up to 95 % yield and with high diastereoselectivities) from a variety of benzyl, heteroaryl, allyl and alkyl alcohols via one-pot alcohol oxidation-Wittig reaction. The transformation utilizes air as the stoichiometric oxidant, and the inexpensive catalyst can be recovered and reused. Filter and use again! Porous manganese oxide molecular sieve based catalysts were found to efficiently promote the oxidation of a variety of alcohols to the aldehydes, which reacted insitu with stabilized Wittig reagent, providing almost exclusively E-α,β-unsaturated esters in good to excellent yields. The heterogeneous catalyst used was made from inexpensive starting materials, and the recovered catalyst was found to be reusable with a modest loss in activity.