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),, 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 a-diketone series only the [2.l.l]dione (70) is , and [2.2.2]Triblattanes 2277Demjanov procedure via 15/16r'71 or even 93% using the Schollkopf sequence via 13/14"'] was achieved. Scheme 2. i) N2HCC02Et/n-butyllithium/THF/-78 to -3 0 T / 97%.ii) C3H5Pd(I)C1 dimer/CH2Clz/-78 to room temp./96%. -iii) NaHC03/H20/150"C/1 h/100%.iv) TMSCN/Zn12/CH2C12. -v) LiAIHdTHF.vi) NaN02/H20/glacial acetic acid/iv-vi: 81 YO