The Pagodane → Dodecahedrane Concept–Shorter Routes, Higher Yields

Abstract

Two variants of the "S 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 functionalizations. The prohibitively low kinetic acidity of "caged" hydrogens has so far only been overcome with the recently reported P 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 2 track.

C20 Carbon Clusters: Fullerene–Boat–Sheet Generation, Mass Selection, Photoelectron Characterization

“…Increasingly economic routes to 5, [27] the isolation of crystalline 6 and 7 and their metal complexation, [28] the failure to isolate or to directly identify 8, 9, and 10, and the liberation of intact C 20 ions with hydrogen contents as low as C 20 H 4 through electron-impact-induced defunctionalization of increasingly higher functionalized dodecahedranes, have been the subjects of detailed publications. [21,29] Herein we present the full account [30] of the vapor-phase production and PE spectroscopic characterization of 1.…”

Towards Perfunctionalized Dodecahedranes—En Route to C20 Fullerene

“…125 8C, averaged elemental composition C 20 H 11.0 Br 7.9 ; [27] ), which was soluble in standard organic solvents, were isolated. IR: ñ = 2928 (CÀH), 1637 (C= C + , 886 (7), 810 (38) …”

“…[3] However, when later the opportunity arose to mass-select and PE spectroscopically characterize the C 20 fullerene, [2] the ratio of the C 20 À /C 20 H À ions as secured from 29 ( Figure 4 b (a)) was too unfavourable to allow a sufficiently neat separation under the then available apparative situation. A much improved protocol for the preparation of starting material 2 [38] provided the encouragement to resume the project, which could easily have ended as just another "exercise in preparative futility". [39] Initially, attempts were made to reduce the hydrogen content of 29 through HBr elimination with the P 2 F base (!…”

The Vibrational Inelastic Neutron Scattering Spectrum of Dodecahedrane: Experiment and DFT Simulation

“…The synthesis and characterization of the dodecahedrane have been discussed. [1,2] The sample was 260 mg of high-purity solid dodecahedrane in an aluminum foil sachet contained in an aluminum cell for protection. The cell was mounted in a cryostat held at 15 K. Data were collection for 20 h with ISIS operating at about 180 mA of proton current.…”