Palladium-Catalyzed Cascade Oligocyclizations Involving Competing Elementary Steps Such as Thermal [1,5]-Acyl Shifts

Tokan, Wajdi M, Schweizer, Stefan, Thies, Claudia, Meyer, Frank E, Parsons, Philip J and de Meijere, Armin (2009) Palladium-Catalyzed Cascade Oligocyclizations Involving Competing Elementary Steps Such as Thermal [1,5]-Acyl Shifts. Helvetica Chimica Acta, 92 (9). pp. 1729-1740. ISSN 0018-019X

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Abstract

Palladium(Pd)-catalyzed oligocyclizations of 2-bromotetradec-1-ene-7,13-diynes with an unsubstituted terminal acetylene moiety like 3 and 5 and 15-bromohexadec-15-ene-3,9-diyn-2-ones like 4 and 6 afforded fulvene derivatives 20 and 21 (Scheme 7) and bis(cyclohexane)-annulated methylenecyclopentene systems 16 and 18 (Schemes 5 and 6), respectively. These transformations constitute cascades of cyclizing carbopalladation steps with ensuing [1,5]-sigmatropic H-atom and acyl shifts, respectively (Scheme 8). In contrast, analogous substrates with one three-atom and one four-atom tether between the unsaturated C,C-bonds, such as 1 and 2, behave differently in that the Pd-substituted hexa-1,3,5-triene intermediates 12 undergo a 6p-electrocyclization instead of a 5-exo-trig carbopalladation followed by ß-hydride elimination to furnish tricyclic bis-annulated benzene derivatives 13 and 14 (Scheme 4).

Item Type: Article
Schools and Departments: School of Life Sciences > Chemistry
Depositing User: Philip Parsons
Date Deposited: 06 Feb 2012 20:45
Last Modified: 30 Nov 2012 17:08
URI: http://sro.sussex.ac.uk/id/eprint/27967
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