Stereoselective Intramolecular Cyclization of Allyl and Homoallyl Benzamide via π-Allylpalladium Complex Catalyzed by Pd(0)

Abstract

The transformation of acyclic allylic benzamides 4 and homoallylic benzamides 12 to vinyl oxazolines 3 is achieved in the presence of base by the catalysis of Pd(0) in high yield and with high diastereoselectivity. Especially, in the case of homoallylic benzamides 12, trans-oxazolines 3 are formed exclusively or predominantly over cis-oxazolines 8, irrespective of the composition of their stereoisomers. The reaction is believed to proceed via the same π-allylpalladium complex that arises from either primary or secondary allylic acetates. We applied this method to the syntheses of β-amino-α-hydroxy acids 1 and γ-amino-β-hydroxy acids 2, conveniently protected as oxazoline.

Iron/Caffeine as a Catalytic System for Microwave‐Promoted Benzamide Formation

“…( S )‐ N ‐Benzoylphenylglycinol (3ac): 23 1 H NMR (300 MHz, [D 6 ]DMSO): δ = 8.70 (d, J = 8.0 Hz, 1 H), 7.91 (d, J = 6.8 Hz, 2 H), 7.62–7.43 (m, 3 H), 7.40 (d, J = 7.2 Hz, 2 H), 7.32 (t, J = 7.4 Hz, 2 H), 7.23 (t, J = 7.1 Hz, 1 H), 5.09 (dd, J = 13.6, 7.9 Hz, 1 H), 4.94 (s, 1 H), 3.83–3.57 (m, 2 H) ppm. 13 C NMR (75 MHz, [D 6 ]DMSO): δ = 166.2, 141.4, 134.7, 131.2, 128.2, 128.1, 127.4, 127.0, 126.8, 64.6, 56.0 ppm.…”

Cytotoxic and Anti-HIV Principles from the Rhizomes of Begonia nantoensis

“…18,19) Fraction 4 was chromatographed on silica gel column with a gradient of i-Pr 2 O-MeOH (49 : 1 to pure MeOH) to give 2-(2-hydroxytricosanoylamino)-1,3,4-hexadecanetriol (28 mg), 20) methylparaben (1 mg), 21) p-hydroxybenzaldehyde (4 mg), 21) and trans-docosanylferulate (15 mg). 22) Fraction 5, on repeated chromatography on silica gel column with a gradient of i-Pr 2 O-MeOH (49 : 1 to pure MeOH) afforded cucurbitacin B (4, 60 mg), 23) dihydrocucurbitacin B (5, 5 mg), 24) cucurbitacin E (6, 18 mg), 4) dihydrocucurbitacin E (7, 4 mg), 23) cucurbitacin I (8, 3 mg), 4) dihydrocucurbitacin I (1 mg), 4) 3b,22a-dihydroxyolean-12-en-29-oic acid (10, 5 mg), 25) indole-3-carboxaldehyde (15 mg), 26) indole-3-carboxylic acid (11, 4 mg), 27) 5,7-dihydroxychromone (12, 4 mg), 28) (S)-N-(1-hydroxymethyl-2-phenylethyl)-benzamide (5 mg), 29) vanillic acid (4 mg), 9) piperonylic acid (1 mg), 30) benzoic acid (20 mg), 31) and caffeic acid (2 mg). 15) The concentrated EtOAc layer (16 g) was subjected to column chromatography over silica gel and eluted with a gradient of i-Pr 2 O-MeOH (5 : 1 to pure MeOH) to give nine fractions.…”

Ring-Construction/Stereoselective Functionalization Cascade: Total Synthesis of Pachastrissamine (Jaspine B) through Palladium-Catalyzed Bis-cyclization of Bromoallenes

“…We expected that palladium(0)-catalyzed cyclization of bromoallenes 19 bearing hydroxy and benzamide groups as internal nucleophiles could regio- and stereoselectively provide appropriately functionalized tetrahydrofuran 18 for synthesis of pachastrissamine 17 (Scheme ). The bicyclic structure of 18 including the exo-olefin would be useful for stereoselective construction of a C-2 stereogenic center as well as carbon homologation.…”