MMPP magnesium

Scheme 7. Preparation of 6,6,6-Trifluoro Analogs of D-Amicetose and D-Rhodinose. (a) AcCl, pyr.j (b) lipase PS (c) TBS-C1, imidazole (d) MMPP (Magnesium monoperoxyhthalate)/. C2c...

The synthesis of rofecoxib can be achieved by several different routes (Drugs Fut., 1998). A highly efficient synthesis for rofecoxib was recently described (Therien et al., 2001). As illustrated in Scheme 79, acetophenon (i) is prepared according to the literature, by Friedel-Crafts acylation with thioanisole. Oxidation with MMPP (magnesium monoperoxyphthalate hexahydrate) affords the sulfone (ii), which is reacted with bromine in chloroform in the presence of a trace amount of AICI3, to give (iii). Bromoketone (iii) is than coupled and cyclized in a second step, one-pot procedure with phenylacetic acid. Firstly, the mixture of bromoacetophenone (iii) and phenylacetic acid in acetonitrile is treated with... 

Chemoselective oxidation of sulfenimines 2 is a useful method for the preparation of sulfinimines 3.10-12 The oxidation was usually carried out with m-CPBA (3-chlo-roperbenzoic acid) in a biphasic mixture of chloroform and aqueous sodium bicarbonate and a variety of sulfinimines have been prepared in this way. Sulfinimines 3 were usually obtained as a single -isomer despite the fact that their precursors 2 may exist as mixtures of E- and Z-isomers.10 Other oxidants which have been demonstrated to be effective for oxidation include MMPP (magnesium monoperoxyphthalate)13 and chlorine.14,15... 

MMPP = magnesium monoperoxyphthalate Fernandez, R. Gasch, C. Lassalwtta. J-M. Llera, J-M. Vazquez, J. Tetrahedron Lett., 1993, 34, 141... 

MMPP magnesium monoperoxyphthalate TBAF tetrabutylammonium fluoride... 

MMPP = magnesium monoperoxyphtbalate Enders. D.i Plant, A. SynLett, 1990, 725. 

The choice of the oxidant is primordial, as it acts both as the nucleophile and the leaving group. A reactivity order of oxidants has been established [174]. Peracids and especially m-CPBA [296] are the most efficient oxidants for the Baeyer-Villiger reaction, followed by alkyl peroxides. The reaction with peracids proceeds faster under acid catalysis [297], but buffered solutions can also be used. Some ketones are un-reactive under standard conditions, and need to be transformed into their hemiketals [298]. Safer peracids such as MMPP (magnesium monoperphthalate) [299, 300] and sodium perborate [301] have also been applied giving similar results as m-CPBA. Recently, processes with solid-supported peracids [302] and transformations in the solid state [303] have been developed. 

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