Gold(I)‐Catalyzed Intramolecular Cycloisomerization of Propargylic Esters with Furan Rings

Abstract

A gold-catalyzed intramolecular cycloisomerization of α-yne-furans 1 is described in this contribution. A variety of cyclic α,β-unsaturated aldehyde or ketone derivatives and nitrogen-containing tricyclic adducts were obtained selectively in moderate to excellent yields under mild conditions by varying the substituents on the standard substrates.

Heteroarene‐tethered Functionalized Alkyne Metamorphosis

“…Surprisingly,t reatment of 218 with 5mol % catalysta tr oom temperature resulted in the formation of ni-trogen-containing tricyclic adduct 221 via [4C+ +3C] cycloaddition pathway (Scheme 55). [66] In 2013, Li et al developed ah ighly regioselective strategy for the synthesis of multi-substituted a-hydroxyallenes 224 from g-(2-pyridyl)-propargyl ethers 222 by using Zirconium complex. Initial formationo fa llenylzirconium intermediate 223 was observed which upon basification yielded the multi-substituted allenes 225 (Scheme 56).…”

“…Surprisingly, treatment of 218 with 5 mol % catalyst at room temperature resulted in the formation of nitrogen‐containing tricyclic adduct 221 via [4C+3C] cycloaddition pathway (Scheme 55). [66] …”

Pentannulation of Heterocycles by Virtue of Precious Metal Catalysis

“…Gold‐catalyzed intramolecular cycloisomerization of an α ‐yne‐furan bearing propargylic ester ( 79 ) afforded α,β‐unsaturated methyl ketone 80 whose treatment with HOTf led to cyclopentanone 81 (Scheme ) . By carrying out this transformation in one pot, the product was isolated in 80 % yield.…”

Gold(I)-Catalyzed Reactivity of Furan-ynes with N-Oxides: Synthesis of Substituted Dihydropyridinones and Pyranones

“… 4 Gold(I) carbenes obtained from propargyl esters were later employed by Tang and Shi in intramolecular reactions with furans, achieving the synthesis of functionalized N -heterocycles and O -bridged tricyclic scaffolds ( Scheme 1 b). 5 Another relevant class of Au(I) carbenes is represented by α-oxo gold(I) carbenes. These reactive intermediates can be accessed by treatment of an alkyne with either a pyridine or quinoline N -oxide in the presence of a Au(I) complex, through nucleophilic attack of the O atom of the N -oxide onto the gold-activated triple bond and subsequent cleavage of the pyridine or quinoline ( Scheme 1 c).…”