Intramolecular Enantioselective Palladium-Catalyzed Heck Arylation of Cyclic Enamides.
Palladium-catalyzed intramolecular cyclization of N-formyl-6-[3-(2-iodophenyl)propyl]-1,2,3,4-tetrahydropyridine (1a) and N-formyl-6-[2-(2-iodophenyl)ethyl]-1,2,3,4-tetrahydropyridine (1b) in the presence of AsPh(3) resulted in formation of the spiro compounds N-formyl-3,3',4,4'-tetrahydrospiro[naphthalene-1(2H),2'(1'H)-pyridine] (2a) and N-formyl-3',4'-dihydrospiro[indan-1,2'(1'H)-pyridine] (2b), respectively, and in the presence of PPh(3) and TlOAc in the spiro compounds N-formyl-3,4,5',6'-tetrahydrospiro[naphthalene-1(2H),2'(1'H)-pyridine] (3a) and N-formyl-5',6'-dihydrospiro[indan-1,2'(1'H)-pyridine] (3b), respectively. Cyclization of N-formyl-6-(3-{2-[(trifluoromethanesulfonyl)oxy]phenyl}propyl)-1,2,3,4-tetrahydropyridine (7) in presence of a chiral (phosphinoaryl)oxazoline ((S)-8) resulted in formation of (R)-3a and (R)-N-formyl-1',3,4,6'-tetrahydrospiro[naphthalene-1(2H),2'(3'H)-pyridine] ((R)-6a) in high enantiomeric excesses, 87% and >99%, respectively, and in good yield. The oxazoline ligand (S)-8 furnished higher enantiomeric excesses and improved regioselectivities than (R)-BINAP.
Ripa
Lena
L
Department of Organic Pharmaceutical Chemistry, Uppsala Biomedical Center, Uppsala University, Box 574, SE-751 23 Uppsala, Sweden.
Hallberg
Anders
A