An atom-economic protocol for the
efficient and highly chemo- and
stereoselective trans-hydroarylation of ynamides
with hydroxyarenes catalyzed by B(C6F5)3 has been developed. Use of readily available starting materials,
low catalyst loading, mild reaction conditions, a broad substrate
scope, ease of scale-up, and versatile functionalizations of the enamide
products make this approach very practical and attractive.
The development of an efficient and straightforward method for cyanation of alcohols is of great value. However, the cyanation of alcohols always requires toxic cyanide sources. Herein, an unprecedented synthetic application of an isonitrile as a safer cyanide source in B(C6F5)3-catalyzed direct cyanation of alcohols is reported. With this approach, a wide range of valuable α-aryl nitriles was synthesized in good to excellent yields (up to 98%). The reaction can be scaled up and the practicability of this approach is further manifested in the synthesis of an anti-inflammatory drug, naproxen. Moreover, experimental studies were performed to illustrate the reaction mechanism.
Ring-opening of bicyclo[1.1.0]butanes (BCBs) is emerging as a powerful strategy for 1,3-difunctionalized cyclobutanes synthesis. However, the reported radical strain-release reactions are typically plagued with diastereoselectivity issues. Herein, an atom-economic protocol for the highly chemo- and diastereoselective polar strain-release ring-opening of BCBs with hydroxyarenes catalyzed by π-acid catalyst AgBF4 has been developed. Use of readily available starting materials, low catalyst loading, high selectivity (up to >98:2 d.r.), a broad substrate scope, ease of scale-up, and versatile functionalizations of the cyclobutane products make this approach very attractive for the synthsis of 1,1,3-trisubstituted cyclobutanes. Moreover, control experiments and theoretical calculations were performed to illustrate the reaction mechanism and selectivity.
Bicyclo[2.1.1]hexanes (BCHs) are becoming ever more important in drug design and development as bridged scaffolds that provide underexplored chemical space, but are difficult to access. Here a novel silver-catalyzed dearomative [2π+2σ] cycloaddition strategy for the synthesis of indoline fused BCHs from N-unprotected in-doles and bicyclobutane precursors is described. This strain-release dearomative cycloaddition operates under mild conditions, tolerates a wide range of functional groups and is capable of forming BCHs bearing three quaternary carbon centers with up to 99% yield, a longstanding challenge in the field. In addition, a scale-up experi-ment and the synthetic transformations of the cycloadducts further highlighted the synthetic utility.
Transition-metal catalyzed isocyanide insertions is one of the key elemental steps for a variety of isocyanide-based transformations. However, the formal insertions catalyzed by main group catalysts are still in their...
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