Lawesson's reagent-promoted deoxygenation of γ-hydroxylactams or succinimides for the syntheses of substituted pyrroles

Abstract

A new method of Lawesson’s reagent-promoted deoxygenation of γ-hydroxypyrrolidones or succinimides is developed for synthesizing substituted pyrroles, where 92 examples are displayed. This reaction is featured by simple operation, satisfying...

Lawesson's Reagent Promoted Deoxygenation of Anhydrides for the Syntheses of 3‐Substituted and 3,4‐Disubstituted Thiophenes

“…After that, 7 a or 8 a reacted with another molecular of A , promoting the formation of 10 a . 10 a then proceeded a similar pathway with our previously reported LR‐promoted deoxygenation of succinimides, [16] realizing the generation of the desired thiophene 2 a .…”

“…Anhydride 1 a was mono-thiolated by LR to render 4 a, which was easily isomerized to 3 a. Then, 3 a underwent thiolation and desulfurization under the promotion of A rendering 7 a, [16,25] which further isomerized to 8 a. After that, 7 a or 8 a reacted with another molecular of A, promoting the formation of 10 a.…”

“…[15] Recently, our research group found a new application of LR, which is LR-promoted deoxygenation of γhydroxy pyrrolidones or succinimides to generate substituted pyrroles (Scheme 1b). [16] Inspired by this project, we wondered whether other five-membered heterocycles with a similar dicarbonyl moiety with succinimides could render the corresponding aryl heterocycles in the presence of LR. Succinic thioanhydride (STA) is structurally similar to succinimide, except that it is more active and easily ring-opened by a nucleophile to give a thiocarboxylate moiety.…”

“…However, the use of LR have changed dramatically, which include constructing biologically valuable heterocycles, coupling reactions, and the thiolation of natural compounds [15] . Recently, our research group found a new application of LR, which is LR‐promoted deoxygenation of γ ‐hydroxy pyrrolidones or succinimides to generate substituted pyrroles (Scheme 1b) [16] . Inspired by this project, we wondered whether other five‐membered heterocycles with a similar dicarbonyl moiety with succinimides could render the corresponding aryl heterocycles in the presence of LR.…”

Lawesson's Reagent‐Mediated Deoxygenation Reactions

“…The following isomerization and deoxygenation processes led to the generation of pyrroles (Scheme 15). In view of the fact that pyrrolidone, pyrrolidine, and pyrrole are the frequently emerged five‐membered cyclic systems in natural products especially alkaloids, realizing the direct transformations among these ring systems may largely improve the synthetic efficiency toward natural products in different families and may provide solid evidence for biogenetic relationship studies [8b–c] …”