α-Amidoaldehydes as Substrates in Rhodium-Catalyzed Intermolecular Alkyne Hydroacylation: The Synthesis of α-Amidoketones.

We show that readily available α-amidoaldehydes are effective substrates for intermolecular Rh-catalyzed alkyne hydroacylation reactions. The catalyst [Rh(dppe)(C6 H5 F)][BArF 4 ] provides good reactivity, and allows a broad range of aldehydes and alkynes to be used as substrates, delivering α-amidoketone products. High yields and high levels of regioselectivity are achieved. The use of α-amidoaldehydes as substrates establishes that 1,4-dicarbonyl motifs can be used as controlling groups in Rh-catalyzed hydroacylation reactions.

Recent applications in natural product synthesis of dihydrofuran and -pyran formation by ring-closing alkene metathesis.

In the past two decades, alkene metathesis has risen in prominence to become a significant synthetic strategy for alkene formation. Many total syntheses of natural products have used this transformation. We review the use, from 2003 to 2015, of ring-closing alkene metathesis (RCM) for the generation of dihydrofurans or -pyrans in natural product synthesis. The strategies used to assemble the RCM precursors and the subsequent use of the newly formed unsaturation will also be highlighted and placed in context.