Ruthenium‐Catalyzed Synthesis of Highly Substituted Pyrroles from 1‐Vinylpropargyl Alcohols and Amines

Abstract

Ruthenium‐catalyzed atom‐economic transformations of 1‐vinylpropargyl alcohols with amines leading to highly substituted pyrroles in a one‐pot cascade process are reported. The allylation/cycloisomerization sequence is catalyzed by a single ruthenium(0) complex that contains a redox‐coupled dienone ligand and can be extended by an additional [3,3] rearrangement. The environmentally benign reactions allow the metal‐catalyzed conversion of inexpensive and readily accessible materials to highly functionalized pyrroles with water as the only waste product.

Ruthenium‐Catalyzed Synthesis of 2,3‐Cyclo[3]dendralenes and Complex Polycycles from Propargyl Alcohols

“…Ruthenium‐catalyzed transformations of propargyl alcohols provide atom‐economic access to many important classes of compounds 6. 7 Recently, we were able to report that cyclopentadienone ruthenium complexes of type 1 (Figure 1) catalyze the allylation and subsequent cyclization or cycloisomerization of heteroarenes, amines, or 1,3‐dicarbonyl compounds with 1‐ene‐4‐yn‐3‐ols ( 2 ), which are easily accessible from α,β‐unsaturated ketones 7a–c. Our previous studies have shown that the metal–ligand bifunctionality of the catalysts is of crucial importance for the course of the cascade reaction (Scheme ) 7a–f.…”

“…7 Recently, we were able to report that cyclopentadienone ruthenium complexes of type 1 (Figure 1) catalyze the allylation and subsequent cyclization or cycloisomerization of heteroarenes, amines, or 1,3‐dicarbonyl compounds with 1‐ene‐4‐yn‐3‐ols ( 2 ), which are easily accessible from α,β‐unsaturated ketones 7a–c. Our previous studies have shown that the metal–ligand bifunctionality of the catalysts is of crucial importance for the course of the cascade reaction (Scheme ) 7a–f. Cyclo[3]dendralenes with no structural flexibility are obtained from doubly allylic propargyl alcohol 2 a and cyclic dicarbonyl compounds 3 in very good yields (Scheme ) 7b.…”

Iron Cyclopentadienone Complexes: Discovery, Properties, and Catalytic Reactivity

“…[9] More recently, the reactivity of parent ruthenium cylopentadienone Ru4 was extended to other types of processes not related to hydrogen transfers, as shown in the recent work of Haak and co-workers on cascade reactions (Scheme 3). [10] This potent hydrogen-bond acceptor catalyst can efficiently activate various propargyl alcohols via p-complexes p-Ru4 a,b, which follow different pathways depending on the substrate substitution pattern. The overall catalytic cycle, involving an internal redox isomerization process, leads to divergent substitution-cyclization sequences by reaction with various nucleophiles.…”

Transition‐Metal‐Catalyzed Transformations of 1‐Alkenylpropargyl Alcohols and Esters: Valuable Cascade Reactions for Increasing Structural Complexity

“…A closely related conversion of tertiary 1‐alkenylpropargyl alcohols 1v (R 3 ≠ H) with various amines to obtain highly substituted pyrroles 109 is catalyzed by redox‐coupled ruthenium(0) complexes 41 (Scheme a) . Formation of alkynyl intermediates 111 is very likely, because conversion of internal alkyne substrates leads to aminoenynes liberated from 110 .…”