Oxidation by Chemical Manganese Dioxide. Part 3.1 Oxidation of Benzylic and Allylic Alcohols, Hydroxyarenes and Aminoarenes

Azobenzenes—synthesis and carbohydrate applications

“…The use of manganese dioxide (MnO 2 ) for the oxidation of aniline derivatives 4 and 5 in refluxing hexane was realized to furnish the corresponding azobenzene analogues 1 and 6 in 69 and 61% yields, respectively (Scheme 2). 19 More recently, Gilbert et al reported the dimerization of 4-chloroaniline (5) via oxidation with MnO 2 in refluxing toluene to afford the corresponding azo compound 6 in a lower yield (49 vs 61%). 20 Starting from the aniline derivatives 7-9 having halogen atoms in the meta or para position, application of this procedure permitted the formation of the corresponding azobenzene analogues 10-12 in 89, 88, and 79% yields, respectively (Scheme 3).…”

Total synthesis of (±)-Anastatins A and B

“…Intermediates 3 and 4 could be prepared by Suzuki coupling of the two bromo apigenin derivatives 5 and 6 with an aryl boronic acid and subsequent removal of the deprotection groups. The required bromo precursors can be derived by monobromination of apigenin (7), which could be readily prepared from the commercially available starting material phloroglucinol (8).…”

Manganese Dioxide Mediated Stereoselective, One‐step Synthesis of Novel Steroidal (6R)‐Spiro‐1',2′,4′‐triazoline‐3′‐thiones

“…[1][2][3][4][5] There have been some reports in the literature on the cyclization of different steroidal as well as non-steroidal aldehyde and ketone thiosemicarbazones under different reaction conditions, which give substituted thiadiazoles, [6][7][8][9][10] triazoline thiones [11][12][13][14] and triazolidine thiones. [15][16][17] Triazoline thiones can be prepared by traditional methods such as the oxidative cyclization of ketone thiosemicarbazones by chromatographic adsorbents like alumina, 11 the boiling of acyl derivatives of thiosemicarbazones with sodium hydroxide, 12 the treatment of alkyl thiosemicarbazide with fluoroalkylcarboxylic acids, 13 and heating carbohydrazides with orthoformate.…”