Diastereoselective synthesis of tetrahydropyranes via Ag(i)-initiated dimerization of cinnamyl ethers

Abstract

We present herein the first synthesis of tetrahydropyranes promoted by a silver salt. Cinnamyl ethers undergo a formal dimerization affording the target heterocycle via sequential C-O bond cleavage/C-H bond functionalization....

Base-promoted Conia-ene cyclization of propargyl amides

“…In this context, our interest in the efficient cyclization of π-systems 6 prompted us to investigate the base-promoted annulation of propargyl amides 1 for the synthesis of highly functionalized pyrrolones and pyrrolidinones 2 under mild, metal-free conditions (Scheme 1c). In this communication, we present our recent findings on a t BuOK-promoted Conia-ene type cyclization that generally proceeds with a catalytic amount of base and it requires minimal reaction times to consume the substrate.…”

“…The pathways proposed in Scheme 2 were derived upon DFT modeling of the involved steps, using a method that proved accurate to describe catalytic sequences and cascades of reactive organic intermediates. 6 The acidity of the protons of 1a was investigated comparing the relative stability of three carbanions I–III , which derived from the formal deprotonation of the acetylenic, propargylic and α-amido protons, respectively. The latter anion is the most stable one (Δ G = −2.9, −3.1 and −7.7 kcal mol −1 , respectively).…”