Studies in the cycloproparene series. On the polarity of alkylidenecycloproparenes

Studies in the Cycloproparene Series: Unexpected Products from Peterson Olefinations

“…Thus, the fluorenylidene derivatives 14 and 15 are available in good yields [14] although no simpler cyclopentadienylidene analogues are known Ϫ the facile thermal dimerisation of cyclopentadienone has precluded its use. In our study of ''push-pull' electronic effects in the cycloproparenes, [15] we attempted to prepare the tetracyclone derivative 16 for use as a model compound by employing what are now conventional procedures and workup.…”

“…The combined organic extracts were washed (water; 3 ϫ 20 mL), dried (MgSO 4 ), filtered, and concentrated under reduced pressure to give a crude product that was purified by radial chromatography. Hydroxytetraphenylcyclopenta-1,3-dienyl)-1-trimethylsilyl-1H-cyclopropa[b]naphthalene (17): Treated as described above, disilane 20 (100 mg. 0.35 mmol), [21] tetracyclone (135 mg, 0.35 mmol) and potassium tert-butoxide (40 mg, 0.35 mmol) gave an orange-brown solid, which upon radial chromatography (light petroleum/dichloromethane, 4:1) gave 1H-cyclopropa[b]naphthalene [14] (2) as the most mobile fraction. Yield 8 mg, (16% Reaction of Silanol 17 with Dilute Hydrochloric Acid: During the space of 1 min an aqueous solution of HCl (10% v/v, 0.5 mL) was added dropwise to silanol 17 (30 mg, 0.05 mmol) in refluxing THF (20 mL).…”

The Fulvalenes

“…The synthesis of these compounds employs Peterson olefination of a ketone using a silyl-substituted cycloproparenyl anion and derivatives Scheme 17. 95-97 are stabilised by the arene fusion. [150,151] The molecules are polar and the crystal structures of 95 and 96 have been determined. [152] Despite these various studies parent 4 has not yet been prepared.…”

“…[182] Reaction of the 1-(trimethylsilyl)cycloproparenyl anion with suberone or benzo[d]cycloheptatriene leads to the arene-fused triaheptafulvalenes 136-138 (Scheme 27) by analogy to the synthesis of 95-97. The molecules are polar but the polarity is small and in the range 1.2-1.6 D. [150,151] Scheme 26.…”

Aryl-substituted methylidenecyclopropa[b]naphthalenes: synthesis and attempted silver(I)-mediated dimerization

“…1 and 2, [1][2][3] have continued to provide a source of fascination 4 since their discovery in 1984, 5 not least because the various derivatives have unexpected polarities, [6][7][8] fluorescence characteristics, 9 and unusual properties. 4,10,11 Recently, we described five protocols that allow for the synthesis of an extensive series of 1-aryl-and 1-diaryl-methylidene-1H-cyclopropa [b]naphthalenes, their polarities, and the linear dependence of their cycloproparenyl 13 C NMR chemical shifts upon the Hammett σ p + constant of the remote aryl substituent.…”