Oxidations - Carbohydrates: Tools for Stereoselective Synthesis - page 321

polyepoxides that were used in this study could be obtained from the epoxidation
of the corresponding polyene with ketone 1 (an example is shown in Scheme
15.11). 1)

Scheme 15.11 Synthesis of tetrahydropyran ring system 36.

Replacing the 4,5-acetonide ketal of ketone 1 with more electron-withdrawing
oxazolidinone or diacetates led to more robust ketones 37 and 38, presumably
(at least partially) due to the reduction of Baeyer-Villiger decomposition (Figures
15.6 and 15.7) [86, 87]. When 5 mol.% (1 mol.% in some cases) of ketone 37 was
used, the epoxidation results obtained were comparable to that of when 20-30 mol.%
of ketone 1 was employed (Figure 15.6) [86]. Diacetate ketone 38 was found to
be an effective catalyst for the epoxidation of

-unsaturated esters, which are
electron-deficient substrates and react sluggishly when ketone 1 is used (Figure
15.7) [87].

α , β

Figure 15.6

Examples of epoxidation of olefins with oxazolidinone ketone 37.

Figure 15.7 Examples of epoxidation of α , β -unsaturated esters with diacetate ketone 38.

1) For more synthetic applications using ketone 1, see Reference [15] and references therein.