Stereoselectivity with neighboring group participation

At first glance, the requirement for the use of already functionalized alkanes seems to limit the applicability of the directed C-H activation approach. However, the utility of such a method is obvious for chemists familiar with the use of auxiliary groups during stereoselective synthesis (neighboring group participation was also applied in the total synthesis shown in Scheme 6). 

Most reports on diastereoselective oxidation of sulfides are substrate-directed. Diastereoselectivity has been achieved by either steric- or neighboring-group participation.21 Incipient hydrogen bonding between the substrate hydroxyl group and the incoming percarboxylic acid has been evoked to explain the high diastereoselectivity observed in the oxidation of 10-exo-hydroxy-bornyl- derivatives 7 and 9 (Scheme 1). The oxidation of 9 with m-CPBA in MeOH occurs without stereoselectivity. 

Cleavage of an acyloxy-carbon bond is possible with a trialkylsilane and TiCU, if it is assisted by neighboring-group participation (Eq. 135) [333] or if it is promoted by release of the strain of a small-ring lactone (Eq. 136) [334-337]. Fairly good stereoselectivity was recorded. 

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