Gold‐Catalyzed Synthesis of Chroman, Dihydrobenzofuran, Dihydroindole, and Tetrahydroquinoline Derivatives

Abstract

Different furans containing an ynamide or alkynyl ether moiety in the side chain were prepared. The gold-catalyzed transformation of these compounds delivered dihydroindole, dihydrobenzofuran, chroman, and tetrahydroquinoline derivatives at room temperature through very fast reactions. Furthermore, the stabilizing effect of the heteroatom directly attached to the intermediate arene oxides led to highly selective reactions, even in the case of only mono-substituted furans, which is quite different from previous results obtained with non-heteroatom-substituted alkynes.

Synthesis of Cyclobutanones via Gold‐Catalyzed Oxidative Rearrangement of Homopropargylic Ethers

“…(4)]. These results indicate that a gold carbenoid should be the key intermediate [23] and pyridine N-oxide can act as a ligand to temper the reactivity of the gold catalyst. [24,25] Additionally, cis-2a could be isolated in 52% yield with 45% ee when 1a with 52% ee was employed [Eq.…”

Synthesis of dihydrobenzofurans and dihydroindoles by intramolecular Friedel-Crafts reaction of aryloxy- and arylamino-substituted propargylic alcohols

“…Propargyl alcohols 1 and 3 are first converted into the allenylic cations I in the presence of Lewis acid via a Meyer-Schuster rearrangement. 4 Then, benzene ring acts as the nucleophile to trap the cation I and form the corresponding dihydrobenzofuran and dihydroindole. …”

“…1,2 Although several general methods for their synthesis have been developed, [3][4][5][6][7][8][9][10][11][12] they often suffer from the use of expensive transition-metal catalysts or toxic reagents and multistep preparation of the starting materials. Hence, efficient and general methods for the synthesis of both dihydrobenzofurans and dihydroindoles from easily accessible starting materials using inexpensive and low-toxicity catalysts are still needed.…”

Taking Advantage of the Ambivalent Reactivity of Ynamides in Gold Catalysis: A Rare Case of Alkyne Dimerization

“…Gold salts or gold complexes, which are strong alkynophilic species, [2] are particularly efficient catalysts for such transformations, as reported in a series of recent articles. [3,4] Following our previous work in this field, [4] we report herein an unprecedented mode of reactivity where, in the presence of a gold(I) complex, ynamides can play the role of both the electrophilic and nucleophilic partner to produce various complex, dimerized products. The formation and the nature of the dimeric products appear to be dependent on the electronic nature of the substituents located on the nitrogen atom and at the alkyne terminus.…”