Functionalized Enantiomerically Pure [1.1.1]‐, [2.1.1]‐, [2.2.1]‐, and [2.2.2]Triblattanes

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 D 3 ‐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[8.4.0.0 2,7 ]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.