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McNamara, OA,Buckley, NR,O'Leary, P,Harrington, F,Kelly, N,O'Keeffe, S,Stack, A,O'Neill, S,Lawrence, SE,Slattery, CN,Maguire, AR
2014
September
Tetrahedron
Catalyst and substituent effects on the rhodium(II)-catalysed intramolecular Buchner reaction
Published
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Optional Fields
COORDINATION CHEMISTRY EFFICIENT SYNTHESIS ALPHA-DIAZOKETONES ARYL DIAZOKETONES DIAZO-COMPOUNDS CARBOXYLATES PRODUCTS CYCLOHEPTATRIENES CYCLOPROPANATION CHEMOSELECTIVITY
70
6870
6878
Intramolecular rhodium(II)-catalysed aromatic addition (Buchner) reactions of a range of alpha- and beta-substituted alpha-diazoketones are reported. Both steric and electronic effects are evident for the aromatic additions investigated. In general, highly efficient aromatic addition is achieved through use of rhodium carboxylates bearing electronegative ligands, such as rhodium trifluoroacetate, while aromatic addition employing rhodium catalysts with more electron-donating ligands, such as rhodium caprolactam, is less efficient. Excellent levels of diastereoselectivity are possible for this process in the presence of rhodium acetate and rhodium caprolactam, however, a reduction in diastereocontrol is generally associated with use of the more reactive, electronegative catalysts. Interestingly, these catalyst effects can be overcome through the steric effects of the substituents on the alpha-diazoketone substrates, with the presence of sterically bulky substituents at the 2- or 3-position rendering the aromatic addition essentially catalyst independent in terms of efficiency and diastereocontrol. (C) 2014 Elsevier Ltd. All rights reserved.
10.1016/j.tet.2014.07.033
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