Starting Material 2,6-Dihetero-adamantanes

For symmetry reasons adamantanes with the sole (R ) or both (R and R ) leaving groups anti to the heteroatom Y(6) were classified and therefore already discussed in 3.2.2. as compounds of the general type G 36 (exchange of the two heteroatoms). 

Starting Material 2,7-Dihetero-isotwistanes and -twistanes as Well as 

With respect to the orientation of the leaving group no isotwistanes, twistanes and homotwistbrendanes (see 3.1.) are known so far as having both leaving groups anti to the heteroatom Y, which could exhibit neighboring group participation. 

Compounds with one leaving group (R ) anti to X(2) and a second (R ) anti to like adamantanes G 54 [R -C(4) R isotwistanes G 55 [R  

R -C(IO) ] andhomotwistbrendanesGJd [R -C(4) R -C(6) ] hav6 two possibilities for neighboring group participation either involving X(2) or Y (see, the general scheme ). 

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