Proton coupling constants in methycyclopentadienes

Ruthenium‐Catalyzed Cross Metathesis of β‐Myrcene and its Derivatives with Methyl Acrylate

“…2‐Methyl‐cyclopenta‐1,3‐diene (6) : A typical experiment was performed in dichloromethane at 80 °C for 18 h. The mixture was cooled to RT, concentrated in vacuo, and purified by Kugelrohr distillation to yield the desired product as a colorless oil according to Korenevskii and Sergeyev and Nicole et al . 1 H NMR (500 MHz, CDCl 3 ): δ =2.02 (dt, 4 J H−H =1.9 Hz, 4 J H−H =1.5 Hz, 3 H, CH 3 ), 2.95 (m, 2 H, CH 2 ), 6.00 (m, 1 H, CH), 6.41 ppm (m, 2 H, CH=CH); 13 C NMR (126 MHz, CDCl 3 ): δ =15.2 (CH 3 ), 41.4 (CH 2 ), 126.8 (CH), 133.7 ( C H=CH), 135.8 (CH= C H), 142.2 ppm (C).…”

Synthesis of New Functionalized Cyclopentadienes To Reach Reversible Bonding between Two Substrates

“…The 1 H NMR data of the isomers 3a and 3b was close to those of the corresponding methylcyclopentadiene isomers, which have already been published. 14,16 In the 2¢substituted major isomer 3a, the 5¢-CH 2 signal appeared as a sextuplet (J = 1.5 Hz) due to coupling with H1¢, H3¢, and H4¢ cyclopentadienyl protons and with the chain 11-CH 2 ; the 11-CH 2 signal appeared as a quadruplet (J = 1.6 Hz) of triplets (J = 7.6 Hz) due to coupling with the 10-CH 2 and long-range coupling with the cyclopentadienyl protons 5¢-CH 2 and H1¢. In the minor isomer 3b, the 5¢-CH 2 was only coupled with H2¢, H3¢, and H4¢ cyclopentadienyl protons and appeared as a quadruplet, and 11-CH 2 was only long-range coupled with H2¢ and appeared as a doublet of triplets.…”

“…Alcohol 3 was a 57:43 isomeric mixture of the 2¢-isomer 3a and the 1¢-isomer 3b of the cyclopentadiene moiety (Scheme 1) and this isomer distribution is similar to that for methylcyclopentadiene. 14,15…”

Enantioselective Ene Reaction of Cyclopentadiene and α,β‐Enals Catalyzed by a Diphenylprolinol Silyl Ether

“…The 5-substituted 1,3-cyclopentadiene unit would be formed by this mechanism and then readily isomerize to the more stable 1-and 2-substituted isomers. [14,15] An intramolecular Diels-Alder reaction was investigated as a synthetic application of these ene products. [16] Cyclopentadiene derivatives 7 a and 8 a were treated with a Wittig reagent to afford trans a,b-unsaturated esters 12 and 13, respectively, in good yield.…”

“…[16] Cyclopentadiene derivatives 7 a and 8 a were treated with a Wittig reagent to afford trans a,b-unsaturated esters 12 and 13, respectively, in good yield. Although the 1-and 2-substituted cyclopenta-1,3dienes 12 and 13 were formed and isolated, the 5-substituted isomer 14 was not detected, [14] but the Diels-Alder reaction proceeded via the latter in toluene at 120 8C to afford tricyclic compound 15 stereoselectively in 68 % yield (Scheme 3). As the Diels-Alder reaction proceeded from the most reactive In summary, we have discovered the first enantioselective intermolecular ene reaction that uses a,b-enals as the enophile, is catalyzed by diphenylprolinol silyl ether, and affords chiral cyclopentadienes as versatile synthetic intermediates.…”