Synthesis and reactions of a new 1,1-disubstituted cyclopentadiene.

Abstract

Dedicated to Prof. Julio Alvarez-Builla on the occasion of his 65 th anniversary AbstractThe synthesis and several synthetic transformations of methyl 1-benzylcyclopenta-2,4-diene-1-carboxylate are described.

An Entry to Functionalized 2,8-Ethanonoradamantane Derivatives

“…Oxidation of 20 with Pd(OAc) 2 in DMSO at room temperature for 16 h gave enone 21 in 87% global yield from ketone 19 , after purification by column chromatography (Scheme ) . Worthy of note and contrarily to our previous experience, oxidation of 20 by using a catalytic amount of Pd(OAc) 2 (5–10%) and oxygen, , or by using Pd(OAc) 2 (0.5 equiv) plus benzoquinone (0.5 equiv) as in the original method of Saegusa, , gave a low yield of 21 (25 and 53% yield, respectively).…”

“…To favor the intramolecular cycloaddition in compound 2 , we then planned the preparation of 2 (R = COOMe) using a methodology we had previously used to prepare methyl 1-benzylcyclopenta-2,4-diene-1-carboxylate . Reaction of alcohol 13 with mesyl chloride in CH 2 Cl 2 in the presence of Et 3 N gave mesylate 17 in 97% yield (Scheme ).…”

“…Reduction of the ketone function of 21 with NaBH 4 in the presence of CeCl 3 ·7H 2 O (Luche conditions), under similar conditions to those used for the preparation of a related compound, , gave a stereoisomeric mixture 22 , derived from the reduction not only of the ketone but also of the imide functions (Scheme ). To study the possibility of carrying out a chemoselective reduction of 21 , we performed this transformation under different conditions, using an excess of CeCl 3 ·7H 2 O, taking into account the possible preferential coordination of the imide function, and reducing the amount of NaBH 4 until 0.5 mol NaBH 4 /mol 21 , always working at −40 °C for 15 min.…”

Generation and Reactions of an Octacyclic Hindered Pyramidalized Alkene

“…Reaction of 31 with the less electrophilic, but much more readily available, dienophile, 2-iodoethynyl(phenyl)iodonium triflate, 24 in acetonitrile at reflux for 64 h, followed by treatment with NaI/CuI, did not give the expected diiodide 34. Reaction of 34 with methanol catalyzed by K 2 CO 3 gave in good yield the corresponding diol 35, which was transformed into the corresponding bismesylate 36 on reaction with MsCl in the presence of Et 3 N. Reaction of 36 with NaI in acetone at reflux gave the tetraiodide 37 in good yield.…”

“…1 H NMR (400 MHz, CDCl 3 ): δ = 0.96 [s, 9H, C(CH 3 ) 3 ], 1.37 (overlapped dd, 2 J (H,H) = 14,8 Hz, 3 J (H,H) = 2.8 Hz, 1H) and 1.39 (overlapped dd, 2 J (H,H) = 14.8 Hz, 3 J (H,H) = 2.8 Hz, 1H) (18-H a and 18-H b ), 1.41 (overlapped dd, 2 J (H,H) = 14.0 Hz, 3 J (H,H) = 2.8 Hz, 1H), and 1.43 (overlapped dd, 2 J (H,H) = 14.0 Hz, 3 J (H,H) = 2.8 Hz, 1H) (2-H a and 2-H b ), 1.50 (s, 1H, 10-H), 1.57 (d, 3 J (H,H) = 6.0 Hz, 1H, 11-H), 1.63 (d, 4 J (H,H) = 1.6 Hz, 1H, 19-H), 1.68 (s, 1H, 9-H), 1.77−1.81 (complex signal, 2H, 3-H and 17-H), 2.22−2.24 (broad s, 1H, 4-H), 2.27 (d, 3 J (H,H) = 6.0 Hz, 1H, 12-H), 2.30 (broad s, 1H, 13-H), 2.38 (broad s, 1H, 16-H), 2.41−2.43 (broad s, 1H, 7-H), 5.95 (dd, 3 J (H,H) = 5.6 Hz, 4 J (H,H) = 3.2 Hz, 1H, 5-H), 6.03 (overlapped dd, 3 J (H,H) = 5.6 Hz, 4 J (H,H) = 3.2 Hz, 1H, 15-H), 6.05 (overlapped dd, 3 J (H,H) = 5.6 Hz, 4 J (H,H) = 3.2 Hz, 1H, 14-H), 6.24 ppm (dd, 3 J (H,H) = 5.6 Hz, 4 J (H,H) = 3.2 Hz, 1H, 6-H). 13 Reaction of Diiodide 38 with Na/Hg in the Presence of 11,12-Dimethylene-9,10-dihydro-9,10-ethanoanthracene 14: Isolation of (3s,4R,7S,8R,9S,10s,11R,12S,13R,16S,17s,19s)-Octacyclo[10.6.1.0 1,10 .0 3,7 .0 4,9 .0 8,19 .0 11,16 .0 13,17 6,24 .0 1,28 .0 2,30 .0 3,18 .0 3,27 .0 4,16 .0 4,25 .0 5,13 .0 6,15 .0 8,12 .0 9,14 .0 16,23 .0 17,21 .0 20,27 .0 22,…”