[3,3] Ring Rearrangement of Oxo- or Aza-Bridged Bicyclo[3.2.1]octene-Based 1,5-Dienes

Abstract

We report that oxo-or aza-bridged alkylidenemalononitrile-cycloheptenes undergo a [3,3] ring rearrangement to yield cyclopenta-fused dihydro-furans or pyrroles. Described herein are the origins of the serendipitous discovery, scope studies, and representative functional group interconversion chemistry.

Vicinal stereocenters via asymmetric allylic alkylation and Cope rearrangement: a straightforward route to functionally and stereochemically rich heterocycles

“…In addition to the exploration of achiral alkylidenemalononitriles 1a–1f (Schemes 1 and 2), prochiral alkylidenemalononitriles 1g–1i were also investigated (Scheme 3). 53,54 For these substrates, we observed a high degree of enantioselectivity with respect to asymmetric allylic alkylation, but an ∼50 : 50 mixture of 1,5-diene diastereomers: the chiral-racemic carbanions generated by deprotonation of 1g–1i couple at equivalent rates with the chiral-nonracemic Pd-π-allyl intermediates, thus yielding enantioenriched diastereomers epi- 3u–3ee and 3u–3ee (Scheme 3A). These diastereomers were resolved through a Cope rearrangement to yield products 4u–4ee (maximum theoretical yield of 50%).…”