[1.1.1]-, [2.1.1]-, [2.2.1]-, [2.2.2]Triblattanes
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
The methylene (2, 7, 10) and spirocyclopropane derivatives (8, 11, 12) are made accessible from rac-trishomocubane(mono-, di-, tri-)ones and optically pure unsaturated and benzoannulated [2.1.1]- (19, 48), [2.2.1]- (30, 53), and D3-symmetrical [2.2.2]triblattanes (3, 4) from the enantiomers of these ketones by expeditious (one pot) ring enlargement and olefination procedures. In the case of the central [2.2.2]trienes (+)-3/( - )-3, novel members of the (CH)14 family, optical resolution is advantageously postponed to the stage of the intermediate [2.2.2]triones (35, 41) and effected via their (R,R)-2,3-butanediol acetals. In the α-diketone series only the [2.1.1]dione (70) is sufficiently stable to allow isolation; tetrone 73 and hexone 5 are indirectly identified as quinoxalines 74 and 76, respectively. Tribenzo[2.2.2]triblattane ( - )-4 is established as the M-helical enantiomer by X-ray crystallography. Generally the thermal stabilization pathway of unsaturated and benzoannulated triblattanes is a [4 + 2] cycloreversion with the primary cycloreversion products [e.g. (1α,2α,7α,10α)-tricyclo[8.4.0.02,7]tetradeca-3,5,9,11,13-pentaene (78) from rac-3] being unstable under the drastic reaction conditions required. The stereochemical course of the perepoxidation of rac-3 is investigated.
Type of Medium: