Palladium-catalyzed diacyloxylation

The catalytic cycle of the palladium-catalyzed diacyloxylation follows the cycle depicted in Scheme 8-6 (X = RCOO, Y = R COO ). The coordination of a quinone in the Ji-allyl)palladium intermediate was demonstrated by NMR studies including T, measurements [58]. Attack by the second nucleophile results in the formation of the 1,4-addition product and a palladium(0)-benzoquinone complex. In an independent mechanistic study, it was shown that such Pd(0)-benzoquinone complexes, which are stable at neutral conditions (pH 7), react with weak acids to give hydroquinone and the palladium(II) salt of the acid [Eq.(36)] [59],... 

A palladium-catalyzed intramolecular lactonization was used as a key step in the enantioselective synthesis of paeonilactones A and B (Scheme 11.38) [127]. Intramolecular 1,4-diacyloxylation of the cyclohexadienylacetic add 101 afforded 102, which was hydrolyzed to 103 this in turn was transformed to 104 in a Mitsunobu reaction. Hydrolysis of 104 to 105 and stereoseledive alkylation afforded 106, which was converted to paeonilactone A. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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