Acid-catalyzed hydrolyses indene oxides

The cis/trans hydrolysis ratio from the acid-catalyzed hydrolysis of indene oxide (53a, Scheme 17) is 75 25,62,63 and that from acid-catalyzed hydrolysis of 5-met-hoxyindene oxide (53b) is 80 20.61 Thus, the introduction of a methoxy group into position 5 does not result in any significant change in the cis/trans hydrolysis ratio. There is evidence that 54b, which is stabilized by the 5-methoxy group, is sufficiently stable to be trapped by external nucleophiles. The very similar cis/tram diol product ratio from acid-catalyzed hydrolyses of both 53a and b suggest that 54a is also a discrete intermediate. 

The stereochemical outcomes of the acid-catalyzed hydrolyses of 1,2,3,4-tetrahy-dronaphthalene 1,2-oxide 59a and its 6-methoxy derivative 59b (Scheme 18) are quite different from those of the corresponding indene oxide systems. For example, acid-catalyzed hydrolysis of 59a yields only 5% of cis diol 61a and 95% of tram diol 62a.66 However, acid-catalyzed hydrolysis of its 6-methoxy derivative 59b yields 80% of cis diol 61b and 20% of tram diol 62b.67 One might argue that carbocation 60a does not have a sufficiently long lifetime compared to solvent relaxation, whereas 60b does, and that this difference in lifetime leads to different mechanisms... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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