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7783475 
Journal Article 
Synthetic applications of manganese dioxide 
Silva da Junior; Eufranio Nunes 
2008 
1 
Synlett
ISSN: 0936-5214
EISSN: 1437-2096 
1 
149-150 
English 
WOS:000252773000032 
(A) Abe et al. showed the first total synthesis of quinolactacide. The synthetic route was concluded with reaction of the dehydrogenation with manganese dioxide in a mixture of chloroform and N,N-dimethylformamide. 5 (Chemical Equation Presented) (B) Taylor et al. reported the first 'tandem oxidation process' (TOP) sequence for the synthesis of bromodienoate esters. Oxidations with MnO2 followed by Wittig reactions have been extensively explored for the elaboration of alcohols to give conjugated alkenes, without the need to isolate the intermediate aldehydes.6 (Chemical Equation Presented) (C) Taylor and co-workers also described the manganese dioxide tandem oxidation-olefination-cyclopropanation sequence, in which the alcohol is treated with MnO2, phosphorane, and sulfurane, respectively. The oxidation-olefination reaction is followed by in situ cyclopropanation of the intermediate γ-ketocrotonate.7 (Chemical Equation Presented) (D) Ramasamy et al. reported the MnO2 oxidation of a thiazoline to a thiazole but also with elimination of the 2′,3′-benzoate groups to form a furan ring. When they tried the dehydrogenation of the thiazoline intermediate with N-bromosuccinimide, followed by the addition of DBU, they also obtained the reaction product of the elimination of the 2′,3′-benzoate groups. The formation of the elimination product of the thiazoline intermediate may have occurred through a radical intermediate. This is the first report where elimination of benzoate groups under radical conditions is shown.8 (Chemical Equation Presented) (E) The TOP sequence developed by Taylor was used coupled with the Bestmann-Ohira reagent. Usingp-nitrobenzyl alcohol (1 equiv), MnO2 (5 equiv), Bestmann-Ohira reagent (1.2 equiv), and K2CO3 (2 equiv) in THF-MeOH (1:1) at r.t. for 18 h, the terminal alkyne was obtained in 89% isolated yield.9 (Chemical Equation Presented) (F) Firouzabadi et al. showed that the use of MnO2 in the absence of solvent has been applied successfully for the oxidation of benzylic alcohols to give the corresponding aldehydes or ketones in excellent yields. Aromatic allyl alcohols were oxidized by MnO2 in excellent yields to the corresponding carbonyl compounds in the presence of 2 molar equivalents of the reagents. 10 (Chemical Equation Presented) (G) Shaabani et al. reported that indans are converted into the corresponding α-ketones in good yields at room temperature in the absence of solvent and under microwave irradiation. The products obtained under these conditions are identical to those obtained from heterogeneous reactions where the oxidant is dispersed in dichloromethane. 11 (Chemical Equation Presented) © Georg Thieme Verlag Stuttgart.