Remote neighboring group effects

Molander has documented an innovative transformation involving an acetal intermediate that allows control over the installation of a remote stereogenic center through the operation of a neighboring group effect (Scheme 6.14) [44]. Treatment of acetal 72 with TMSOTf produces an oxocar-benium ion 73, which is trapped by the proximal methyl ether to form 74. Subsequent attack by cyanide affords nitrile 76 in 15 1 dr. 

In organic chemistry it is well known that a substituent directly linked to a reaction center has a profound effect on the latter s reactivity. The influence of a remote substituent has also received much attention as more organic molecules are being scrutinized. Thus, neighboring group participations in solvolysis are generally observed. Certainly, the full attribution of a substituent must be the sum of electronic, steric, and stereoelectronic factors. 

A. V. Demchenko, E. Rousson, and G.-J. Boons, Stereoselective 1,2-cw-galactosylation assisted by remote neighboring group participation and solvent effects, Tetrahedron Lett., 40 (1999) 6523-6526. 

More remote secondary isotope effects, such as y-d effects, cannot be generalized, and thus each effect requires a specific explanation. An example of the use of a combination of a-, jS-, and y-d effects in the study of participation by the neighboring aryl group is included below to represent the use of these effects in studies of neighboring groups. The interpretations presented are the reported ones rather than our own. 

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