Palladium catalyzed synthesis of poly-substituted and poly-functionalised conjugated 1,3-dienes from allyl bromides and α-diazoesters†
Abstract
Conjugated dienes and polyenes are important moieties in biology and pharmaceuticals. Typically, they are prepared by sequential introduction of C–C bonds. Here we report straightforward access to 1,1,3,4-tetrasubstituted conjugated dienes from allyl bromides and α-diazoesters at room temperature. The reaction is compatible with various electron donating and electron withdrawing substrates flaunted on both allyl bromides and α-diazoesters. In addition, the reaction tolerates various bromide substituted reactants which may pave the path for later stage functionalization. Along the line, in the case of bromide derivatives, the oxidative addition is selective towards allyl bromide C(sp3) even in the presence of aromatic bromide C(sp2). Mechanistically, the reaction is proposed to follow a pathway involving the formation of a π-allylic palladium carbene complex and subsequent migratory insertion.
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