Enantioselective preparation of 3-substituted 4-pentenoic acids via the Claisen rearrangement

Mechanistic Studies of Wacker-Type Intramolecular Aerobic Oxidative Amination of Alkenes Catalyzed by Pd(OAc)2/Pyridine

“…To a solution of 47 (1.1 g, 11 mmol) in a 2:1 (volume ratio) mixture of THF and HMPA, a solution of LDA (6.1 mL 1.8 M in THF, 11 mmol), was added slowly via syringe at −78 °C under an N 2 atmosphere. After stirring for 30 min at −78 °C, 1-Bromo-2-butyne (1.6 g, 15 mmol) was added to the mixture solution 38. The mixture was stirred for 3 hours at −78 °C, and then was warmed to room temperature.…”

Table of Contents

“…Heterocycles of 1,3‐azoles are important synthetic intermediates, and undergo extensive chemical transformations involving nucleophilic addition of the CN bond or nucleophilic ring‐opening,19 sodium‐alcohol reduction then acid hydrolysis to aldehyde,20 base hydrolysis to organic acid,21 and thermal rearrangement to 2‐bromodifluoromethylisocyanates 22. Therefore, functionalisation of the 1,3‐azolic moiety could provide possibilities for construction of a new generation of gem ‐difluoromethylene‐linked identical or nonidentical twin drugs.…”

A direct and rapid route to α,α-difluoroacylsilanes from trifluoroethanol

“…Toluene performed rather poorly when used to replace benzene (an heterogeneous mixture was formed at the concentration specified in the literature) as the reaction solvent, and the cost of the ADDP reagent was considerable. Instead, chloride 10 was synthesised [22] from the monobenzyl ether [23] of commercial Z-buten-1,4-diol and treated with the sodium salt of trifluoroethanol in THF, as described by Metcalf (method E), in the first instance to afford the ether in 73% yield (Fig. 3).…”

“…Literature procedures were used to prepare 1-(benzyloxy)-4-chloro-2Z-butene 10 [22,23] and 5-bromo-penta-1,3E-diene [30].…”

“…for C 6 H 9 F 3 O 154.06005]; m/z (EI) 154 (62%, M + ), 139 (78%, M + -CH 3 ).3.6. Preparation of 4-(2 0 ,2 0 ,2 0 -trifluoroethoxy)-1-(benzyloxy)-but-2Z-ene (5f) From trifluoroethanol (3.99 g, 40 mmol), potassium hydroxide (4.32 g, 77 mmol) in water (18 mL) and 1-(benzyloxy)-4-chloro-2Z-butene 10[22,23] (5.23 g, 27 mmol) at 85 8C for 24 h. The usual work up and distillation (Kugelrohr) afforded ether 5f as a colourless liquid (5.6 g, 81%, 100% by GC); bp 70 8C/0.04 mmHg, R f (5% diethyl ether in light petroleum ether) 0.35; n max (film)/ cm À1 : 3032s, 2929m, 1496s, 1454s, 736s, 697s; d H (300 MHz; CDCl 3 ) 7.38-7.35 (5H, m, C 6 H 5 ), 5.93-5.83 (1H, m, HC=CH), 5.78-5.68 (1H, m, HC=CH), 4.53 (2H, s, PhCH 2 O), 4.20 (2H, d, J = 6.3, OCH 2 CH=), 4.10 (2H, d, J = 6.6, OCH 2 CH=), 3.79 (2H, q, 3 J H-F = 8.8, CF 3 CH 2 ); d C (75 MHz; CDCl 3 ) 138.1, 131.0 (two signals), 128.5, 127.9 (two signals), 124.1 (q, 1 J C-F = 279.5), 72.5, 67.8, 67.3 (q, 2 J C-F = 34.0), 65.6; d F (282 MHz; CDCl 3 ) À74.0 (t, 3 J F-H = 8.8); [HRMS (ES + , M + Na + ) Found: 283.0932. Calc.…”