Enantioselective diene Cyclization/Hydrosilylation catalyzed by optically active palladium bisoxazoline and pyridine-oxazoline complexes.
A 1:1 mixture of (N-N)Pd(Me)Cl ¿N-N = (S,S)-4,4'-dibenzyl-4,5,4', 5'-tetrahydro-2,2'-bisoxazoline (S,S-4a) and NaBAr(4) ¿Ar = 3, 5-C(6)H(3)(CF(3))(2) (5 mol %) catalyzed the asymmetric cyclization/hydrosilylation of dimethyl diallylmalonate (2) and triethylsilane at -30 degrees C for 48 h to form an 8.1:1 mixture of the silylated carbocycle (S,S)-trans-1, 1-dicarbomethoxy-4-methyl-3-¿(triethylsilyl)methylcyclop ent ane (S, S-3) (95% de, 72% ee) and dimethyl 3,4-dimethylcyclopentane-1, 1-dicarboxylate (S,S-6) in 64% combined yield. In comparison, a 1:1 mixture of the palladium pyridine-oxazoline complex (N-N)Pd(Me)Cl ¿N-N = (R)-(+)-4-isopropyl-2-(2-pyridinyl)-2-oxazoline (R-5b) and NaBAr(4) (5 mol %) catalyzed the asymmetric cyclization/hydrosilylation of 2 and triethylsilane at -32 degrees C for 24 h to form carbocycle S,S-3 in 82% yield (>95% de, 87% ee) as the exclusive product. Asymmetric diene cyclization catalyzed by complex R-5b was compatible with a range of functional groups and produced carbocycles with up to 91% ee. The procedure also tolerated substitution at a terminal olefinic position and at the allylic position of the diene.
Perch
N S
NS
Duke University, P. M. Gross Chemical Laboratory, Durham, North Carolina 27708-0346, USA.
Pei
T
T
Widenhoefer
R A
RA
D001896:Boron Compounds / Q000138:chemical synthesis*; D002384:Catalysis; D003517:Cyclopentanes / Q000138:chemical synthesis / Q000737:chemistry*; D003998:Dicarboxylic Acids / Q000138:chemical synthesis / Q000737:chemistry*; D007202:Indicators and Reagents; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D017646:Organosilicon Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010080:Oxazoles; D010165:Palladium; D011725:Pyridines; D013237:Stereoisomerism
C411451:1,1-carbomethoxy-4-methyl-3-((triethylsilyl)methyl)cyclopentane; D001896:Boron Compounds; D003517:Cyclopentanes; D003998:Dicarboxylic Acids; D007202:Indicators and Reagents; D009942:Organometallic Compounds; D017646:Organosilicon Compounds; D010080:Oxazoles; D011725:Pyridines; C411452:dimethyl 3,4-dimethylcyclopentane-1,1-dicarboxylate; D010165:Palladium; C023666:pyridine