Selective Oxidations of Secondary Alcohols in Presence of Primary Alcohols

Abstract

In the 40's, during studies on the preparation of retinene, Ball et al. needed to oxidized vitamin A (76) to the corresponding aldehyde 77. Me Me Me OH Me Me Me Me Me O Me Me H MnO 2 vitamin A (76) 77 A small yield of the aldehyde was obtained using potassium perman-ganate. Therefore, they embarked on a detailed exploration on the experi-mental conditions for best yield. It became apparent that best results were obtained when a dark precipitate of MnO 2 was formed by decomposition of potassium permanganate in aqueous solution. 1 In fact, it was found that vitamin A (76) could be eYciently oxidized by shaking a solution in light petroleum in the presence of an excess of suspended manganese dioxide. DiVerent types of manganese dioxide showed very diverse oxidizing eYciency. It was very fortunate that they prepared manganese dioxide in a Wnely divided very active form by mixing aqueous solutions of manganese sulfate (MnSO 4) and potassium permanganate (KMnO 4), because the com-mercial samples were much less eYcient. Active manganese dioxide was used by Canonica in 1947 2 for the oxidation of oximes into nitrocompounds before the seminal publication of Ball et al. on the oxidation of vitamin A (76). Canonica prepared active manganese dioxide by reacting MnCl 2 with KMnO 4 . In fact the oxidation power of precipitated manga-nese dioxide is known since the 1870's. 3