Gold-Catalyzed cis-Hydroarylation of Ynamides with Indoles: Regio- and Stereoselective Synthesis of a Class of 2-Vinylindoles.

A new gold-catalyzed reaction of ynamides with 3-substituted indoles as nucleophiles is reported. The reaction allows for the synthesis of a new class of 2-vinylindole derivatives in good yields via the intermediacy of a cyclopropyl gold-carbenoid species.

Exploiting the σ-phylic properties of cationic gold(i) catalysts in the ring opening reactions of aziridines with indoles.

A study on the SN2-type ring opening reactions of aziridines with indoles as nucleophiles is reported. Under gold(i) catalysis a great variety of tryptamine derivatives were prepared in good to excellent yields with complete stereocontrol when chiral aziridines were used. We demonstrated that cationic gold(i) catalysts are superior Lewis acids to the previously reported group 3, 12 and 13 metals in terms of catalyst loading and reaction yields. Moreover, complete regioselectivity was observed for 2-phenyl-N-tosylaziridine; whereas, regioselectivity up to 10 : 1 ratio was observed with 2-methyl-N-tosylaziridine. Finally, a preliminary study on the dearomatization reactions giving rise to pyrroloindolines is also reported.

Synthesis of constrained analogues of tryptophan.

A Lewis acid-catalysed diastereoselective [4 + 2] cycloaddition of vinylindoles and methyl 2-acetamidoacrylate, leading to methyl 3-acetamido-1,2,3,4-tetrahydrocarbazole-3-carboxylate derivatives, is described. Treatment of the obtained cycloadducts under hydrolytic conditions results in the preparation of a small library of compounds bearing the free amino acid function at C-3 and pertaining to the class of constrained tryptophan analogues.