title: Cyclic Enecarbamates as Precursors of α,β-Unsaturated Iminium Ions: Reactivity and Synthesis of 6,6-Spirocyclic Ring Systems.
abstract: The scalable synthesis of cyclic enecarbamates and their use as convenient precursors of α,β-unsaturated N-acyl iminium ions is reported. The newly developed route overcomes synthetic and reactivity difficulties in previously reported methods, is readily scaled up, and proceeds through stable intermediates suitable for long-term storage if required. Preliminary investigations probing the reactivity of cyclic α,β-unsaturated N-acyl iminium ions as dienophiles in Diels-Alder reactions and electrophilic alkylating agents are described. In the presence of Lewis and Brønsted acids, iminium precursor 22a underwent efficient Diels-Alder cycloaddition with a range of simple and complex dienes, culminating in the synthesis of 6,6-spirocyclic ring systems possessing the same relative stereochemistry as the spirocyclic imine present in the marine natural product gymnodimine 1.
authors.affiliation: School of Chemical Sciences, University of Auckland , 23 Symonds Street, Auckland 1142, New Zealand.|Maurice Wilkins Centre for Molecular Biodiscovery , 3 Symonds Street, Auckland 1142, New Zealand.
authors.forename: Zhanwei
authors.initials: Z
authors.lastname: Wang
authors.affiliation: School of Chemical Sciences, University of Auckland , 23 Symonds Street, Auckland 1142, New Zealand.|Maurice Wilkins Centre for Molecular Biodiscovery , 3 Symonds Street, Auckland 1142, New Zealand.
authors.forename: Niels
authors.initials: N
authors.lastname: Krogsgaard-Larsen
authors.affiliation: School of Chemical Sciences, University of Auckland , 23 Symonds Street, Auckland 1142, New Zealand.|Maurice Wilkins Centre for Molecular Biodiscovery , 3 Symonds Street, Auckland 1142, New Zealand.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Daniels
authors.affiliation: School of Chemical Sciences, University of Auckland , 23 Symonds Street, Auckland 1142, New Zealand.|Maurice Wilkins Centre for Molecular Biodiscovery , 3 Symonds Street, Auckland 1142, New Zealand.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Furkert
authors.affiliation: School of Chemical Sciences, University of Auckland , 23 Symonds Street, Auckland 1142, New Zealand.|Maurice Wilkins Centre for Molecular Biodiscovery , 3 Symonds Street, Auckland 1142, New Zealand.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Brimble