Asymmetric catalytic hydrogenolysis of aryl-halide bonds in fused arene chromium and ruthenium complexes

Article Article scientifique Article Asymmetric catalytic hydrogenolysis of aryl-halide bonds in fused arene chromium and ruthenium complexes eng 2010 author Mercier Audrey Catherine Marie 663211 author Urbaneja Biosca Xavier 639301 author Yeo Wee Chuan author Chaudhuri Piyali Datta author Cumming Graham R. author House David 520445 author Bernardinelli Gérald Hugues 24765 author Kundig Ernst Peter 26401 6285-6299 10.1002/chem.201000011 0947-6539 Access to highly enantioenriched planar chiral [Cr(5-bromonaphthalene)(CO)3] (6), [Ru(η5-C5R5)(5-bromonaphthalene)][PF6] (42) and [Ru(η5-C5R5)(4-bromoindene)] (44) was sought using asymmetric hydrogenolysis of [Cr(5,8-dibromonaphthalene)(CO)3] (5), [Ru(η5-C5R5)(5,8-dibromonaphthalene)] (39) and [Ru(η5-C5R5)(4,7-dibromoindene)] (40), respectively. Initial efforts focused on the chromium complex 5. Pd0 catalysts with dimethoxyethane as the solvent and LiBH4 or NaBH3CN as a hydride source worked best. Nineteen chiral bidentate phosphorus ligands were screened in this reaction. Asymmetric induction was low to modest with product ee's in the range of 4 to 52 % and yields of 6 of up to 70 %. Chiral phosphoramidite ligands proved superior and a bulky ligand derived from a Whitesell amine and 3,3'-diphenyl-binaphtol afforded 6 with an ee of 97 %. The high enantioselectivity is largely due to the initial desymmetrization reaction though kinetic resolution also plays an important role as shown by the determination of a selectivity factor s=8.5 at -10 °C. Initially high ligand loadings (4 equiv/Pd) were necessary to achieve good asymmetric induction. This could be traced to the trapping of the chiral ligand by borane formed in the reaction. Addition of 1,4-diazabicyclo[2.2.2]octane (DABCO) suppressed this, and its addition led to the use of Pd and chiral ligand in a 1:1.2 ratio. Asymmetric hydrogenolysis of cationic dibromonaphthalene and neutral dibromoindenyl complexes of Ru cyclopentadienyl complexes was investigated and afforded the following results: [RuCp(5-bromonaphthalene)][PF6] (39 a; 75 %, 90 % ee), [RuCp*(5-bromonaphthalene)] [PF6] (39 b; 88 %, 99 % ee), [RuCp(4-bromoindenyl)] (44 a; 72 %, 96 % ee), and [RuCp*(4-bromoindenyl)] (44 b; 62 %, 68 % ee). Asymmetric catalysis Chromium Enantioselectivity Hydrogenolysis Indenyl Naphthalene Ruthenium Dewey 540 36 Département de chimie organique 141 false Chemistry 16 21 5a12904a-5f85-4efd-af74-e381a0efc641 Article (Published version) Restricted fulltext.pdf 624046 application/pdf restrictedAccess Faculté des sciences / Section de chimie et biochimie / Département de chimie organique

Title	Published in	Year	Views	Downloads

Asymmetric catalytic hydrogenolysis of aryl-halide bonds in fused arene chromium and ruthenium complexes	Chemistry	2010	918	0
Catalytic Enantioselective Hydrogenolysis of [Cr(CO)3(5,8-Dibromonaphthalene)]	Angewandte Chemie	2006	631	0

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