Vectononselectivity and Vectoselectivity

Where zero (154a/b) or one vectoplex (155a/b) is involved, every point on one pathway has a homometric counterpart on the other hence, the pathways are exactly superimposable and no selectivity is possible these are cases of vectoaselectivity. Qn the other hand, for per/aper alignments such as those in 156a/b and 157a/b, every point on one pathway has an enantiometric coimterpart on the other in the absence of chiral influences, the pathways are isoenergetic, though obviously not superimposable, and while the resultant transition states/intermediates/products are enantiomorphic, no vectoselectivity is expected - these are cases of vectononselectivity. 

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Figure 13.16. Examples of Vectoaselective, Vectononselective and Vectoselective Processes...

Table 13.1 (p. 134) summarizes the five modes of vectoselectivity at all homotopic (hi-h6), enantiotopic (e), and diastereotopic (di-d4) faces. In Figures 13.22-13.24 are shown examples of vectoaselective, vectononselective and vectoselective transformations of molecules with homotopic, enantiotopic and diastereotopic faces,respectively. 

Figure 13.22. Examples of Vectoaselectivity, Vectononselectivity and Vectoselectivity at Enantiotopic Eaces...

Face hs is vectononselective with respect to e and di, vectoselective with respect to hs, d2, ds and d4 it is vectononselective or vectoselective with respect to he. 

We note, parenthetically, that hi and h4, which had exhibited identical behavior in the vectoselectivity-facioselectivity correlations of Table 13.3 (p. 140), clearly show their differences in face-face selectivities vide supra). With respect to face e, hi is avectoselective or vectononselective h4 can be only vectononselective. 

Face d2 is vectononselective with respect to ds, but vectoselective with respect to d2 and d4. Face ds is vectoselective with respect to ds and d4. Finally, d4 is vectoselective with respect to d4. 

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