Oxidation reactions guanidine-catalysed

Fu, X., Jiang, Z. and Tan, C.-H. (2007) Bicyclic guanidine-catalysed enantioselectivephospha-Michael reaction synthesis of chiral P-aminophosphine oxides and P-aminophosphines. Chemical Communications, 5058-5060. 

The Os(VIII)-catalysed alkaline oxidation of guanidine hydrochloride by 104 ions is of fractional order in OH and zero order in substrate. The rate law for Mn(n)-catalysed oxidation of 2-amino-meto-xylene to 2,6-dimethyl-pura-benzoquinone in acetone-water solution has a complex dependence in H+ the rates decrease on increasing the ionic strength and decreasing the dielectric constant of the medium. The oxidation of myo-inositol has been studied in both alkaline and acidic solution and found to exhibit inverse fractional order in H" " and OH ions the alkaline reaction has an inverse fractional order in the substrate, whereas a fractional order is observed in the acidic reaction. The Ru(III)-catalysed oxidation of 2-methylcyclohexanol (mch) to 2-methylcyclohexan one in HCIO4 is zero order in mch and H" " ions. The rate of oxidation of L-serine to 2-hydroxyethanal in alkaline medium is retarded by OH ions and the ionic strength. ... 

Excellent conversions and selectivities were observed both with respect to the alkene and the primary oxidant [62]. In nitro-Michael reaction it was noted that the Murphy s PTC does not work as a good chiral catalyst for the Michael reaction of chalcone, but the same PTC effectively catalyses the epoxidation of chalcones with sodium hypochlorite (NaOCl) [24c]. Trials for the epoxidation of chalcone in the combination of hydroperoxides and modified guanidines 19 [27b] resulted in less effective asymmetric induction compared to the Murphy s PTC [53] (Scheme 4.21). 

The scope of this mechanism for the reaction of a series of nucleophiles with hydroperoxides has been reviewed and a linear free-energy plot of ogkz against logArj derived for acid-catalysed oxidations. The reaction of l-aIkyl-3-aryl-thioureas with HgOa yields 1,2,4-thiadiazoles which rearrange in acidic solutions to thiazolyl-guanidines. The formation of amidinothioureas as precursors of the thiadiazoles has, however, been established. 

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