A New and Efficient Approach to Cyclic .beta.-Enamino Esters and .beta.-Enamino Ketones by Iodine-Promoted Cyclization

Abstract

The development of new methods for preparing nitrogen five-membered rings, such as pyrrolidine and pyrrole derivatives,* 1 continues to be an active research area, since they are useful intermediates for the synthesis of many natural products.

Silver‐Catalyzed Hydroamination: Synthesis of N‐Bridgehead Pyrroles, Incorporating a Protection‐Deprotection Strategy for Preparation of Cyclic Secondary Vinylogous Carbamates

“…They have been prepared from lactim ethers, [10] from azido dicarbonyl compounds, [11] from alkenyl-substituted β-enamino esters, [12] and by lithiation of ketimines [13] amongst others. However, the most common method used for preparation of these compounds is the Eschenmoser sulphide contraction (also known as the Eschenmoser coupling reaction).…”

Preparações e aplicações sintéticas recentes de enaminonas

“…Nosso grupo de pesquisa, nos últimos anos, tem utilizado a ciclofuncionalização para obtenção de heterociclos oxigenados 38,39 e nitrogenados 40,41 . Em recente trabalho 42 , aplicamos a iodociclofuncionalização em β-enamino ésteres para obtenção de tetraidropiridinas que, após reação de desidroiodação, forneceram ciclopentanos trissubstituídos (Esquema 18).…”

Tellurium and Iodine Promoted Cyclofunctionalization of Alkenyl Substituted β-Keto Esters

“…As an extension of our previous works, 8,9,15 and in analogy to those cited above, we investigated the behaviour of a series of α-and γ-alkenyl-β-keto esters toward aryltellurium trichloride. For comparison purposes, the same substrates were also submitted to treatment with iodine.…”

“…An analogous iodine-promoted cyclization of β-enamino esters and ketones, which led to synthetically valuable precursors for the pyrrole nucleous, has already been described by us. 15 Nevertheless, the tellurocyclofunctionalization of alkenyl β-keto esters appears to be unprecedented.…”