[5 + 1] Annulation:  A Synthetic Strategy for Highly Substituted Phenols and Cyclohexenones

Abstract

A novel [5 + 1] annulation strategy is developed for the synthesis of highly substituted phenols and cyclohexenones from alpha-alkenoyl ketenedithioacetals and nitroalkanes.

Intramolecular Aza‐Anti‐Michael Addition of an Amide Anion to Enones: A Regiospecific Approach to Tetramic Acid Derivatives

“…During the course of our study of a-oxoketene S,Sacetal chemistry, [7] we reported an intramolecular oxo-anti-Michael reaction, in which the carboxyl acid oxygen could regioselectively attack the a-carbon of the b-(2-/4-pyridyl)-substituted enone fragment under acidic conditions, allowing the formation of tetronic acids. [8] However, in that case the anti-Michael addition occurred only in b-(2-/4-pyridyl)-substituted enone substrates; at the same time, the presence of a protonic acid appears indispensable, because the corresponding sodium carboxylate of 4-pyridyl-substituted enones failed in the cyclization reaction, which proved that the 2-/4-pyridinium induced the anti-Michael addition due to a strong ÀC effect (negative conjugation effect).…”

Tandem Double‐Michael‐Addition/Cyclization/Acyl Migration of 1,4‐Dien‐3‐ones and Ethyl Isocyanoacetate: Stereoselective Synthesis of Pyrrolizidines

“…[4] Our research in this area [5,6] has shown that 1,4-dien-3-ones of the type 1 can be used as versatile building blocks for the efficient construction of a wide variety of carbo-and heterocycles. [6] In the present study, treatment of 1,4-dien-3-one 1 a with ethyl isocyanoacetate (2) was performed under basic conditions to test our [5+1] annulation reactions, where 1 a acted as the dielectrophile (Table 1). [6a, b] Pyrrolizidine 3 a was obtained in 83 % yield under optimized reaction conditions, where 1 a (1.0 mmol) was treated with 2 (1.2 mmol) and the reaction catalyzed by DBU (30 mol %) in acetonitrile (5 mL) at 80 8C in air for 0.3 hours ( Under the optimized reaction conditions (Table 1, entry 1), this tandem reaction showed broad tolerance for various R 1 substituents (Table 2).…”

Acidity-Controlled Indolylation of 3, 3-Bis(ethylthio)acrylate

“…为探 索简洁有效的合成方法和新颖的吲哚衍生物, 有机化合 物的吲哚化反应一直受到合成化学家的广泛关注. 易制备和多反应中心的 α-羰基二硫缩烯酮是重要 的有机合成中间体 [14～16] , 在构造芳环 [17,18] 、杂环化合物 的合成 [19～21] 、 多取代烯烃的合成 [22,23] 和作无气味的代硫 [29,30] . 当 1a 与 2 位非取代的吲哚反应时, 在浓 酮 [30] .…”