Binding of unsaturated propellanes to transition metal centers, hexacarbonylmolybdenum-promoted skeletal isomerization of [4.4.2]propella-2,4,11-trienes

Substituent effects in arosemibullvalene photochemistry: the methylcyclopropane rearrangement of 1,8-dimethylbenzosemibullvalene

“…Note that Paquette et al (13) have investigated the benzo-COT/benzobicyclo[4.2.0]-octatriene thermal interconvertibility and additionally have reported an alternative preparation of COT 15. However, 15 was not obtained pure by their route (14).…”

“…It is to be noted that structures such as 26-28, which are a priori alternatives for methylcyclopropane 1 ,4-hydrogen migration products from 14 methyl doublet in the 'Hmr spectrum; 27 and 28 contain nonconjugated dienes.…”

“…Gas phase ti~ertrio(vsis of 14 Over a 1 h period 94.4 mg (0.52 mmol) of 14 was sublimed into a Pyrex tube (30 x 2cm) packed with glass beads (0.5cm diameter) maintained at 420°C. The pressure in the system was kept at 6 Torr by the passage of nitrogen.…”

Synthesis of Highly Enantioenriched Propelladienes and their Application as Ligands in Asymmetric Rh-Catalyzed 1,4-Additions

“…o .0] architecture that embeds three rings cojoined by a central C–C bond . Paquette et al prepared and demonstrated the utility of achiral [4.4.2]­propella-3,11-diene as a chelating diene by the formation of a molybdenum complex (Scheme a) . Recently, our group developed a general asymmetric route to carbocyclic propellanes .…”

A photochemical approach to methyl-substituted 5-oxabicyclo[2.1.0]pent-2-enes (Dewar furans)

“…4 In selecting the photosubstrates (12) and (13) for this work we included a pinching group5 to ensure stability of the bicyclo[4.2.0]octa-2,4-diene moiety6 and to aid the fragmentation step. The syntheses of (12) and (13) outlined in Scheme 2 are novel and utilise the N-methylsuccinimide ring system in this pinching role, rather than the related succinic anhydride as reported by others,' since the N-substituted imides are less prone to competitive photofragmentation.8 The choice of the Dewar benzene intermediates (6) and (7), while daring,? was entirely successful and led to high yields of the adducts (8)$ and (9)$ where the presence of the activated maleimide functionality in (6) and (7) ensured the correct site-selectivity upon reaction with 2,5-dimethyl-3,4-diphenylcyclopentadienone.…”