The gold-catalyzed intermolecular Diels–Alder cycloaddition and competitive Michael addition reactions between 2-vinylindoles and enones/enals are reported. The reaction outcome strictly correlates with the electronic character of the heteroaromatic substrate. Thus, Diels–Alder cycloadducts are the sole products in the presence of less electron-rich heterocycles, whereas Michael addition adducts are
Gold(I)-Catalyzed Synthesis of Tetrahydrocarbazoles<i>via</i>Cascade [3,3]-Propargylic Rearrangement/[4+2] Cycloaddition of Vinylindoles and Propargylic Esters
A gold(I)‐catalyzed cascade [3,3]‐propargylic rearrangement and [4+2] cycloaddition reaction of 2‐vinylindoles with propargylicesters is reported. The reaction leads to the synthesis of highly substituted tetrahydrocarbazole derivatives in high yields and diasteroselectivities. Furthermore, a preliminary screening for an asymmetric version of this reaction is described.
Diels–Alderreactions of 2-vinylindoles with cyclic carbo- and heterodienophiles, in the presence of suitable Lewis acids, led to uncommon [ c ]-carbo- and furoannulated tetrahydrocarbazoles. The obtained compounds encompass a carbonyl group in an angular position, suitable for further transformations, and represent useful intermediates for the synthesis of more complex structures.
The synthesis of cyclohepta[b]indole derivatives through the dearomative (4 + 3) cycloaddition reaction of 2-vinylindoles or 4H-furo[3,2-b]indoles with in situ generated oxyallylcations is reported. Oxyallylcations are generated from α-bromoketones in the presence of a base and a perfluorinated solvent. Cyclohepta[b]indole scaffolds are obtained under mild reaction conditions, in the absence of expensive