Bromoallenes as Synthetic Equivalents of Allyl Dications: Synthesis of Medium-Sized Nitrogen Heterocycles through the Cyclization of Bromoallenes in the Presence of a Palladium(0) Catalyst and an Alcohol

摘要

Medium-sized nitrogen heterocycles (7- to 12-membered rings) are an extremely important class of compounds, which occur in a wide range of natural and non-natural products.~[1] In particular, seven-and eight-membered nitrogen heterocycles are constituents of a number of compounds with interesting pharmacological properties.~[2,3] Cyclization to medium-sized heterocycles is often slow and is hampered by the unfavorable enthalpies (strain in medium rings) and entropies (probability of the chain ends meeting) of the reaction. Accordingly, the construction of medium-sized heterocycles is a popular challenge for synthetic chemists.~[4,5]