The synthesis of bismethylene derivatives of triangulanes

The First Enantiomerically Pure [n]Triangulanes and Analogues: σ-[n]Helicenes with Remarkable Features

“…The 1 H and 13 C NMR spectra of the product were identical to the reported ones. [37] 13 C NMR spectrum of the product was identical to that reported for the racemic compound. [34] (1R,3S) General procedure GP 5: Ethyl diazoacetate (125 mmol) was added dropwise to a stirred solution of the corresponding methylenedispiroheptane (85 mmol) and dirhodium tetraoctanoate (0.6 ± 0.8 mol %) in anhydrous methylene chloride (120 mL) at 0 8C.…”

“…It will also be quite interesting to investigate the Raman optical activities (ROA) of the whole series of enantiomerically pure methylene[n-1]triangulanes and [n]triangulanes, since the ROA of (M)-(À)- [4]triangulane (M)-(À)-3 has been shown to disclose spectacular effects with D values close to 0.5 % in the 900 cm À1 region. [36] Experimental Section General aspects: Racemic bicyclopropylidenecarboxylic acid rac-12, [12] racemic exo-dispiro[2.0.2.1]heptane-1-carboxylic acid rac-13, [13] racemic anti-rac-1-(tetrahydropyranyloxymethyl)-4-methylenespiropentane, [37] racemic 1-methylenedispiro[2.0.2.1]heptane (rac-28), [38] racemic [4]triangulane (rac-trispiro[2.0.0.2.1.1]nonane rac-3), [38] enantiomerically pure anti-(4-methylenespiropentyl)methanols (1R,3S)-and (1S,3R)-18, [18] (6), [39] and (N-tert-butoxycarbonyl)glycine (7) [40] were prepared according to the previously published procedures. The acid rac-12 was purified by column chromatography on silica gel (eluent hexane/Et 2 O 3:2) followed by recrystallization from hexane (rac-12: m.p.…”

“…After an additional 15 min of stirring, a solution of racemic anti-(1RS,3SR)-1-(tetrahydropyranyloxymethyl)-4-methylenespiropentane [37] (9.21 g, 47.4 mmol) in CH 2 Cl 2 (25 mL) was added dropwise at 0 8C over a period of 0.5 h. The mixture was stirred for an additional 2 h at ambient temperature, washed with brine (4 Â 100 mL), dried, and concentrated under reduced pressure at 0 8C. Pentane (100 mL) was added, the mixture was stirred for an additional 2 h, and then filtered.…”

Linear and Branched Phospha[n]triangulanes

“…CuCl (99 % purity) was purchased from Acros and stored under nitrogen before use. (5,6-Dimethyl-2,3-bis(methoxycarbonyl)-7-phenyl-7-phosphanorbornadiene) pentacarbonyltungsten (8), [9,13] methylenespiropentane (9), [28] 1-methylenedispiro-[2.0.2.1]heptane (10), [29] 7-methylenedispiro[2.0.2.1]heptane (11), [29,30] 1,4-bismethylenespiropentane (15), [31] perspirocyclopropanated bicyclopropylidene 18, [3] cyclopropylidenespiropentane (20), [32] 7-cyclopropylidenedispiro[2.0.2.1]heptane (22), [30] and ethenylbicyclopropylidene (25) [33] were prepared according to literature procedures.…”

Spiroannulated Cyclopropanes

“…Zefirov's group reported the synthesis of bis-methylene derivatives of triangulanes 56 which are prospective starting materials for the synthesis of high molecular weight oligomers of spiroannulated cyclopropanes 76 . However, the efficient synthesis of the latter compounds requires development of a method for coupling of various triangulane fragments.…”