Formal Synthesis of (±)-Peduncularine: Use of the [3 + 2] Annulation of Allylic Silanes and Chlorosulfonyl Isocyanate

[reaction: see text] The formal synthesis of the alkaloid (+/-)-peduncularine (1) was accomplished through the use of a [3 + 2] allylic silane annulation. The annulation of cyclohexadienyl silane 6 with chlorosulfonyl isocyanate followed by an in situ reduction provided bicyclic lactam 7. Conversion of this intermediate to 2 in three steps completed the formal synthesis of (+/-)-peduncularine.