Barium manganate preparation

Barium manganate, prepared from potassium manganate and barium chloride [5JJ] or by the reduction of potassium permanganate with potassium iodide in the presence of barium chloride and sodium hydfoxide [5J2], is used for the quantitative oxidation of benzhydrol to benzophenone. The reaction mixture is refluxed in benzene for 0.5-2 h [SJ5]. The result is comparable with and even better than that of oxidation with manganese dioxide [250, 525]. 

A second total synthesis of ascididemin (323) was achieved by Moody et al. in 1990 in two steps starting from l,10-phenanthroline-5,6-quinone (331) (Scheme 38) (155,156). The quinoneimine 333 was first prepared by reaction between the quinone 331 and the sodium salt of diethyl N-(2-iodophenyl)-phosphoramidate (332). Photocyclization of 333 in cone, sulfuric acid gave ascididemin (323). Because of the low yield of especially the first step, 10%, preparation of 333 was carried out via a different route in two steps. The reaction of epoxide 334 with 2-iodoaniline 335 gave the amino alcohol 336, which was readily oxidized with barium manganate to the desired intermediate 333. 

Barium manganate, BaMn04. Mol. wt. 256.28, dark green crystals. Supplier Aldrich. The reagent is prepared by the reaction of aqueous solutions of KMnO (1 equiv.), BaCla (1 equiv.), NaOH (1 equiv.), and KI (0.12 equiv.). The reagent separates as dark green crystals and is dried by azeotropic removal of water with benzene. 

The readily available and stable compound barium manganate has been shown to be an efficient oxidizing agent for the oxidation of primary and secondary alcohols to carbonyl compounds. It has similar activity to manganese dioxide but is claimed to be better for the preparation of certain aldehydes e.g. the furan aldehyde (11) is produced in 80% yield whereas with Mn02 the yield is less than 20%. 

Cyclopentanone has been prepared from adipic acid by distilling the calcium salt,1 heating alone 2 or with acetic anhydride,3 or in the presence of various catalysts such as barium hydroxide,4 thorium oxide,5 manganous oxide,5 uranium nitrate,6 ferrous sulfate 6 and others.7... 

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