Iron-catalyzed δ-selective conjugate addition of methyl and cyclopropyl Grignard reagents to α,β,γ,δ-unsaturated esters and amides

Iron‐Catalyzed Reactions of 2‐Pyridone Derivatives: 1,6‐Addition and Formal Ring Opening/Cross Coupling

“…2-Pyridones are obviousa nd relevantc andidates: [13][14][15] the enamide embedded in their ring system is certainly not ap rivi-leged subunit for classical cross coupling via oxidative insertion/reductive elimination, whereas an iron catalyzed 1,6-addition is feasible since acyclic a,b,g,d-unsaturateda mides have previously been shown to react with aryl-Grignardr eagents in the presenceo fc atalytic amounts of FeCl 2 with high selectivity. [16,17] Indeed, the N-benzylated substrate 1,o nt reatment with PhMgBr and Fe(acac) 3 (5 mol %), gave product 2a in which the heterocyclic ring is intact (Table 1);u nder optimized conditions (THF, À45 8C), the yield was almostq uantitative (entry 6). Fe(acac) 3 ,F e(acac) 2 and FeCl 3 work almoste qually well, [18] whereas the reactiond id not proceed with FeF 3 or in the absence of an iron precatalyst.…”

Noncanonical Strigolactone Analogues Highlight Selectivity for Stimulating Germination in TwoPhelipanche ramosaPopulations

“…During this operation, the reaction continued refluxing without heating. After the addition of the halide was completed, the mixture was stirred at room temperature for 5 h. The titration was performed as described in Sugano et al…”

“…This was used in the next step without further purification but can also be purified by chromatography on silica gel (heptane/EtOAc, 40:60) to afford pure alcohol 22a as an oil: IR (film) ν max 3446, 2973, 2921, 1774, 1677, 1464, 1420, 1374, 1170, 1043, 1015, 975, 908, 839, 796, 690 cm −1 ; 1 H NMR (300 MHz, CDCl 3 ) δ 5.75 (1H, dd, J = 1.0, 15.5 Hz, H-6), 5.59 (1H, dd, J = 8.0, 15.5 Hz, H-7), 4.41 (1H, dd, J = 8.0, 10.0 Hz, H-5a), 3.97 (1H, t, J = 8.5 Hz, H-5b), 3.19 (1H, sext, J = 8.5, H-4), 2.65 (1H, dd, J = 8.5, 17.5 Hz, H-3a), 2.34 (1H, dd, J = 9.5, 17.5 Hz, H-3b), 1.30 (6H, s, H-9 and H-10); 13 Preparation of Cyclopropylmagnesium Bromide. 75 To a stirred suspension of magnesium turnings (300 mg, 12.30 mmol) in dry THF (2.0 mL) under argon was added commercially available cyclopropyl bromide (0.800 mL, 9.99 mmol) in dry THF (12.2 mL) dropwise at room temperature for 30 min. During this operation, the reaction continued refluxing without heating.…”

“…During this operation, the reaction continued refluxing without heating. After the addition of the halide was completed, the mixture was stirred at room temperature for 5 h. The titration was performed as described in Sugano et al 75 (E)-4-(3-Cyclopropyl-3-hydroxybut-1-en-1-yl)dihydrofuran-2(3H)-one (22b). Ground CeCl 3 (455.5 mg, 1.80 mmol, 1.4 equiv) was dried by heating at 140 °C/30 rpm for 2 h. Dry THF (11 mL) was added at 0 °C.…”

Iron-Promoted 1,5-Substitution Reaction of Endocyclic Enyne Oxiranes with MeMgBr: A Stereoselective Method for the Synthesis of Exocyclic 2,4,5-Trienol Derivatives

“…The combined use of iron compounds and Grignard reagents has been widely preferred in metal-mediated nucleophilic substitution [1][2][3][4][5][6][7][8][9][10] and addition [11][12][13][14][15][16][17][18][19][20] reactions. Both reagents are readily available, environmentally friendly, and relatively low in cost.…”