Effect of Allylic CH_3-nF_n Groups (n = 1−3) on π-Facial Diastereoselection

Abstract

[structure: see text]. Michael addition of various enolates toward gamma-CH(3-n)F(n)-alpha,beta-unsaturated ketones (n = 1-3) was proven to smoothly furnish the 1,4-adducts with high si face selectivities which monotonously decreased by reduction in the number of fluorines. Although the Felkin-Anh model correctly anticipates the present stereochemical outcome only with E-acceptors, the hyperconjugative stabilization of transition states by electron donation from the allylic substituents (the Cieplak rule) successfully explains the pi-facial preference of both acceptors at least in a qualitative level.

Synthesis and polymerization of novel fluoroalkyl 2‐trifluoromethylacrylate possessing tetrahydrofuran moiety

“…Hydrolysis of 2-(1,1,3,3,3-pentafluoro-2-benzoxypropyl)tetrahydrofuran was carried out by adding 30 mmol of 2-(1,1,3,3,3-pentafluoro-2-benzoxypropyl)tetrahydrofuran, 30 mL of methanol with 20 mL of water, and 360 mmol of sodium hydroxide under refluxing for 24 h. After the reaction the product was extracted by diethyl ether followed by washing with saturated water solution of sodium chloride and then distilled under reduced pressure to afford 1,1,3,3,3-pentafluoro-1-tetrahydrofuranyl-2-propanol. 1 2-Trifluoromethylacryloyl chloride was synthesized by the reaction of 2-trifluoromethylacrylic acid (1.0 mol) with phthaloyl dichloride (1.0 mol) at 120 C for 2 h. 6,7 The product was collected by fractional distillation. HFIP (Central Glass Co.) was dried by refluxing over calcium hydride and distilled.…”

Synthesis and polymerization of novel bis(2‐trifluoromethylacrylate)

“…1 7,8 by the reaction of 2-trifluoromethylacrylic acid (1.0 mol) with phthaloyl dichloride (1.0 mol) at 120 C for 2 h. The product was collected by fractional distillation; bp: 82 C; yield: 68%. 2-Trifluoromethylacrylic acid supplied by Tosoh F-Tech and phthaloyl dichloride from Iharanikkei were used as received.…”

The effect of fluoromethyl groups on the diastereoselectivity in the electrophilic alkylation

“…1 H NMR (CDCl 3 ): d 1.32 (3H, t, J = 7.05 Hz), 4.28 (2H, q, J = 6.90 Hz), 6.49 (1H, qd, J = 1.80, 15.60 Hz), 6.78 (1H, qd, J = 6.60, 12.00 Hz). 13 …”

“…20,4.05,54.92 Hz),6.30 (1H,dtd,J = 0.90,3.00,15.90 Hz),6.83 (1H,dtd,J = 4.20,10.20,15.90 Hz),m). 13 C NMR (CDCl 3 ) : d 66.88,112.20 (t,J = 236.73 Hz),126.77 (t,J = 10.57 Hz),128.11,128.26,128.38,134.99,136.59 (t,J = 24.07 Hz), 164.08. 19 …”

“…Taking into account the fact that the steric size of a CF 3 group is regarded to be between i-Pr and i-Bu moieties [12], this relatively high syn preference should stem from the electrostatic environmental difference between two p-faces. Further, the Michael addition of various enolates toward g-CH 3Àn F n -a,b-unsaturated ketones [13], was proven to smoothly furnish the 1,4-adducts with high si face selectivities which monotonously decreased by reduction in the number of fluorines. Although the Felkin- Anh model [14] correctly anticipates the present stereochemical outcome only with E-acceptors, the hyperconjugative stabilization states by electron donation from the allylic substituents (the Cieplak rule) explains the p-facial preference of both acceptors at least in a qualitative level.…”