The First Ring-Expansion of a 1-Azabicyclo[1.1.0]butane to a 1- Azabicyclo[2.1.1]hexane

The reactions of 3-phenyl-1-azabicyclo[1.1.0]butane (4) with dimethyl dicyanofumarate ((E)-8) and dimethyl dicyanomaleate ((Z)-8) lead to the same mixture of cisand trans-4-phenyl-1-azabicyclo[2.1.1]hexane 2,3-dicarboxylates (cis-11 and trans-11, resp.; Scheme 3). This result of a formal cycloaddition to the central C-N bond of 4 is interpreted by a stepwise reaction mechanism via a relatively stable zwitterionic intermediate 10, which could be intercepted by morpholine to give a 1 : 1 : 1 adduct 12, which undergoes a spontaneous elimination of HCN to yield the fumarate 13 (Scheme 4). DOI: https://doi.org/10.1002/hlca.200690044 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-54215 Accepted Version Originally published at: Mloston, G; Heimgartner, H (2006). The first ring-enlargement of a 1-Azabicyclo[1.1.0]butane to a 1Azabicyclo[2.1.1]hexane. Helvetica Chimica Acta, 89(3):442-449. DOI: https://doi.org/10.1002/hlca.200690044 Prof. Dr. H. Heimgartner Tel. 01 635 4282 Fax 01 635 6836 e-mail: [email protected] The First Ring-Expansion of a 1-Azabicyclo[1.1.0]butane to a 1Azabicyclo[2.1.1]hexane by Grzegorz Mlostoń* University of Lodz, Department of Organic and Applied Chemistry, Narutowicza 68, PL-90-136 Lodz and Heinz Heimgartner* Organisch-chemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich