Hydrogen bond directed highly regioselective palladium-catalyzed allylic substitution.
The palladium-catalyzed allylic substitution of 5-vinyloxazolidinones and derivatives was investigated. Unusual and high regioselectivity for the branched product was observed. The regioselectivity was influenced by the type of substrate, the solvents, and the nucleophile. Imide-type nucleophiles were found to be directed to the internal carbon (branched:linear, 75:25 to >98:2), whereas sulfonamides, amines, and malonates added only to the terminal carbon of the allyl complex. Relatively nonpolar solvents such as toluene and THF favored the branched product (97:3 and 95:5, respectively). Acetonitrile and dichloromethane afforded lower regioselectivity (50:50 and 67:33, respectively), and the use of the protic solvent ethanol resulted in reversal of the regioselectivity (12:88). The directing group on the substrate was important. Amides afforded almost complete formation of the branched product, and carbamates gave a 50:50 mixture of regioisomers with phthalimide as the nucleophile. Evidence for direction of the nucleophile via hydrogen bonding was obtained by replacing the hydrogen of the amide with a methyl, resulting in the production of only the normal linear product.
Cook
Gregory R
GR
Department of Chemistry, North Dakota State University, Fargo, North Dakota 58105-5516, USA. Gregory.Cook@ndsu.nodak.edu
Yu
Hui
H
Sankaranarayanan
S
S
Shanker
P Sathya
PS
D000498:Allyl Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D006860:Hydrogen Bonding; D023303:Oxazolidinones / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry
D000498:Allyl Compounds; D023303:Oxazolidinones; D014753:Vinyl Compounds; D010165:Palladium