C. Bonaccorsi, A. Mezzetti
Sep 15, 2005
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0
Influential Citations
38
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Journal
Organometallics
Abstract
The dichloro complexes [RuCl 2 (1a)] (2a) and [RuCl 2 (1b)] (2b) with the chiral tetradentate PNNP ligands (1S,2S)-N,N'-bis [o-(diphenylphosphino)benzylidene] cyclohexane-1,2-diamine (1a) and (1S,2S)-N,N'-bis[o-(bis(4-trifluoromethylphenyl)phosphino)benzylidene]cyclohexane-1,2-diamine (1b) react with AgSbF 6 (1 equiv) to give the highly reactive five-coordinate complexes [RuCl(PNNP)]SbF 6 (3aSbF 6 or 3bSbF 6 ), which were characterized in solution. The reaction of 2a or 2b with AgBF 4 gives [RuCl(PNNP)]BF 4 along with unidentified products. Complex [RuCl(lb)]SbF 6 (3bSbF 6 ) cyclopropanates 1-octene to ethyl 2-hexylcyclopropane-1-carboxylate (up to 66% overall isolated yield) in the presence of ethyl diazoacetate with unprecedented cis-diastereoselectivity (85:15 cisztrans ratio) and with excellent enantioselectivity (up to 99 and 98% ee for the cis and trans isomers, respectively). Complex 3bSbF 6 is also an excellent cis-selective cyclopropanation catalyst for styrene (96% ee for the cis isomer, 99:1 cis:trans ratio) and α-methylstyrene (96% ee for the cis isomer, 92:8 cis:trans ratio). The catalyst activity depends on the counterion and increases in the order [BF 4 ] - < [SbF 6 ] - < [PF 6 ] - , whereas the best stereoselectivity is observed with [SbF 6 ] - . Molecular modeling calculations are extended to 1-octene and α-methylstyrene and revised to account for the absolute configuration of ethyl cis-2-phenylcyclopropane-1-carboxylate (1S,2R, incorrectly reported as 1R,2S in a former paper).