A simple approach to the bicyclo[5.3.1]undecane system present in taxanes

Progress in the Construction of Cyclooctanoid Systems: New Approaches and Applications to Natural Product Syntheses

“…Thus, reaction of the tricyclo[5.2.1.0 2,6 ]decane derivative 542 with SmI 2 led smoothly to reductive C 2 −C 6 bond cleavage to furnish 543 quantitatively and in a stereoselective manner . The protocol appears to be fairly general and even liquid ammonia reductions can be gainfully employed as shown by the conversion of 544 to 545 , Scheme 111 …”

“…232 The protocol appears to be fairly general and even liquid ammonia reductions can be gainfully employed as shown by the conversion of 544 to 545, Scheme 111. 233 Magnus and co-workers have created the B ring of taxane via reduction of the internal cyclopropyl bond in the keto ether 546 with sodium naphthalenide to furnish 547 in a highly selective manner and in quantitative yield, Scheme 112. 234 Earliest examples of cyclooctanoid ring construction through oxidative cleavage of bicyclo[3.3.0]oct-1(5)-ene moiety was reported by Mehta et al 235,236 Thus, polyquinanes 548 and 549 were cleaved with RuO 2 -NaIO 4 to 1,5-cyclooctadiones 550 and 551, respectively, Scheme 113.…”

Halogen-assisted alkylation of ester enolates. Facile synthesis of C10-functionalized tricyclo[5.2.1.02,6]decenes

“…Found: C, 43.14; H, 4.33. (iii) With 3-Chloro-2-(chloromethy 1)propene. The alkylation of 3 (500 mg, 1.20 mmol) in THF (4.5 mL) using LDA [prepared from diisopropylamine (0.42 mL, 3 mmol) in anhydrous THF (5 mL) and n-BuLi (1.60 mL, 3 mmol)] with 3-chloro-2-(chloromethyl)propene (188 mg, 1.5 mmol) in the presence of HMPA (0.5 mL, 2.87 mmol) furnished the monoalkylated product 7 (500 mg, 83%), mp 146-148 °C, as an inseparable mixture in a ratio of ca. 1:1: tR (230 °C) 7.16 and 8.24; IR 1740,1600,1130 cm"1; NMR (270 MHz) b 3.09 (d, J = 13.9 Hz, 1 H), 3.27 (d, J = 14.2 Hz, 1 H), 3.56 (s, 3 H), 3.63 (s, 1 H), 3.66 (s, 3 H), 3.68 (s, 3 ), 3.70 (s, 3 H), 3.96 (d, J = 12.3 Hz, 1 ), 4.20 (d, J = 12.6 Hz, 1 ), 5.10 (s, 1 H), and 5.34 (s, 1 H).…”

Carbon-carbon bond cleavage in norbornane derivatives. Convenient route to novel carbocyclic rings

“…For example, the dimethyl esters 15a,b when treated with Na-NH 3 (l) at -55 o C underwent C-C bond cleavage 15 to afford stereoselectively the bridged eight-membered rings 16a,b (Scheme-7). The alkene unit in the product 16a was employed for elaboration to the bicyclo[5.…”