Copper-catalyzed multicomponent reactions for the efficient synthesis of diverse spirotetrahydrocarbazoles

• Shao-Cong Zhan,
• Ren-Jie Fang,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 796–808, doi:10.3762/bjoc.18.80

• [carbazole-2,3'-indolines], spiro[carbazole-3,5'-pyrimidines] and spiro[carbazole-3,1'-cycloalkanes] in satisfactory yields and with high diastereoselectivity. Keywords: Diels–Alder reaction; indole; indolo-2,3-quinodimethane; Levy reaction; tetrahydrocarbazole; spirooxindole; Introduction

• this respect, Lévy reported a copper-catalyzed three-component reaction of aromatic aldehydes, ethyl indole-2-acetate and N-alkylmaleimides for the efficient construction of polycyclic tetrahydrocarbazoles, in which indolo-2,3-quinodimethane intermediate was initially generated and sequentially

• (reaction 2 in Scheme 1) [75][76][77]. It was noticed that only ethyl indole-2-acetate was successfully employed as the precursor to generate the active indolo-2,3-quinodimethane intermediate in the Levy reaction, which greatly limited its practical synthetic value. We envisioned that other substituted