The Pagodane → Dodecahedrane Concept-Shorter Routes, Higher Yields.

Two variants of the "S _N 2 route" from pagodanes (A, B) to functionalized dodecahedranes (D, F) and particularly dodecahedradienes (E) offer considerable improvements in the number of operations (from nine to five to three) and yields (e.g., for diester F from 55-65 to 70-75 to 85-91%). Key steps are the regio- and stereospecific introduction of four to six bromine substituents into dimethyl pagodane-4-syn,9-syn-dicarboxylate (1 b) and a highly complex (thirteen bond-breaking/bond-forming events in four participating structures). yet very convenient (one-pot operation) and extremely efficient (nearly quantitative) transformation of secopagodane to bissecododecahedradiene with complete stereocontrol in transannular CH ₂ functionalizations. The prohibitively low kinetic acidity of "caged" hydrogens has so far only been overcome with the recently reported P ₂ F reagent (Schwesinger). Further improvement of the overall economy of the pagodane → dodecahedrane scheme has been achieved by efficiently channeling a byproduct of the pagodane synthesis (ca. 10%) back into the S _N 2 track.
(Copyright © 1996 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)