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DOI: 10.1055/s-0035-1562467
Configurationally Stable Doubly Bridged Biphenyl Azocines through Copper-Catalyzed Double Carbene Insertions into the Corresponding Azepines
Publication History
Received: 03 June 2016
Accepted after revision: 22 June 2016
Publication Date:
03 August 2016 (online)


In memory of Jean-François Normant
Abstract
Doubly bridged biphenyl azocines can be prepared in a single step through copper-catalyzed reactions of a doubly bridged biphenyl azepine and diazodiester reagents. Double [1,2]-Stevens rearrangements occur at 100 °C to afford doubly tethered eight-membered rings (49 to 61%) as trans and cis regioisomers (1:1 ratio). These products present an axial chirality. ECD and VCD analyses of the separated enantiomers (CSP-HPLC) were used to assign the absolute configuration. High configurational stability is observed for both regioisomers as racemization does not occur after 1 week of heating at 208 °C in dodecane (ΔG ‡ > 41 kcal·mol–1). Interestingly, reactions performed at 40 °C retain a certain level of enantiospecificity (82–86%), avoiding, for the most part, thermal racemization of the starting material.
Key words
azepine - azocine - carbenes - configurational stability - [1,2]-Stevens rearrangement - ylidesSupporting Information
- Supporting information for this article is available online at http://dx.doi.org/10.1055/s-0035-1562467.
- Supporting Information