Palladium(II)‐Catalyzed Isomerization of Olefins with Tributyltin Hydride.

Abstract

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Directed, Palladium(II)-Catalyzed Enantioselective anti-Carboboration of Alkenyl Carbonyl Compounds

“…Compound 1c was isolated as a light-brown oil (908 mg, 41% yield). General Procedure for Alkyne Semireduction 20 and Jones Oxidation: 18 To a stirred solution of alkyne substrate in anhydrous MeOH (0.33 M), were added Lindlar's catalyst (5 mol%) and quinoline (7 mol%). The reaction mixture was stirred under H 2 atmosphere (1 atm) for 3 days at room temperature.…”

“…[α] D 20 = +9.4 (c = 0.35 Chloroform, 86:14 er). SFC (chiral column) The enantiomeric ratio was determined by chiral SFC on a Daicel IB column (3 µm, 4.6×250 mm), 35% MeOH/CO 2 , 4.0 mL/min, λ = 241 nm, t (major) = 2.088 min, t (minor) = 2.499 min.…”

“…Purification using silica gel column chromatography with 4:1 hexanes:EtOAc as the eluent gave the product as a yellow oil (38.1 mg, 79% yield, 91:9 er). [α] D 20 = +16.3 (c = 0.4 Chloroform, 91:9 er). This product was isolated as an inseparable 20:1 mixture of diastereomers.…”

Isomerization of Allylbenzenes

“…On a related theme to these particular allyl group isomerizations, Giles and co-workers applied PdCl 2 (MeCN) 2 to isomerize the stereoisomeric cis / trans mixture of styrenes 343 , formed by a Wittig approach, almost exclusively to the respective ( E )-styrenes 344 (Scheme ) . The topic of E / Z isomerization of alkenes has enjoyed considerable recent interest ,, and has been summarized in two excellent reviews, , and consequently this aspect will remain outside the focus of our Review.…”

Direct Enantioselective and Regioselective Alkylation of β,γ-Unsaturated Carboxylic Acids with Chiral Lithium Amides as Traceless Auxiliaries

“…Notably, ethylation of 3phenyl-3-butenoic acid also occurred at the apparently more hindered α position with good regioselectivity (10:1) and excellent enantioselectivity in 77% yield (3p). Although the 4Z-methyl substituent had no detrimental effect on the reaction outcome (3o), alkylation of (Z)-4-phenyl-3-butenoic acid, 13 while highly regioselective (>20:1), resulted in substantially lower yield and er values (3q). A test of the alkylation procedure on a 1 g scale was performed with (E)-4-(naphthalen-2-yl)-3-butenoic acid, which afforded 3b in excellent yield and excellent enantio-and regioselectivity.…”