Solid-phase synthesis of 4-methylene pyrrolidines and allylic amines using palladium-activated allylic linkers

Abstract

The solid-phase synthesis of 4-methylene pyrrolidines and allylic amines has been achieved using palladium-catalysed nucleophilic cleavage of allylic linkages. Six pyrrolidines were synthesised in five steps from a carboxyethyl resin 20, where the key transformations included a Lewis-acid promoted imino-Sakurai type reaction and reductive alkylation prior to the final palladium-catalysed cyclisation cleavage of the allylic carboxylate linkage. Allylic carboxylate resin 22 was also shown to undergo "traceless" cleavage using various hydride sources in the presence of catalytic palladium. A more robust allylic ether linkage was also investigated. Starting from a phenol resin 36, a number of 3-aryl-allylamines were prepared using a palladium-catalysed nucleophilic cleavage reaction.

Ruthenium(II) Arene Complexes with Asymmetrical Guanidinate Ligands: Synthesis, Characterization, and Application in the Base-Free Catalytic Isomerization of Allylic Alcohols

“…Solvents were dried by standard methods and distilled under nitrogen before use. All reagents were obtained from commercial suppliers and used without further purification, with the exception of the ruthenium(II) arene dimer [{RuCl(μ-Cl)(η 6 - p -cymene)} 2 ], guanidines ( i PrHN) 2 CNR ( 1a – e ), the lithium amidinate salt Li[( i PrN) 2 CMe], and the allylic alcohols 1-(4-fluorophenyl)-2-propen-1-ol, 1-(4-chlorophenyl)-2-propen-1-ol, and 1-(4-methoxyphenyl)-2-propen-1-ol, which were prepared by following the methods reported in the literature. Infrared spectra were recorded on a Perkin-Elmer 1720-XFT spectrometer.…”

“…Solvents were dried by standard methods and distilled under nitrogen before use. All reagents were obtained from commercial suppliers and used without further purification, with the exception of the ruthenium(II) arene dimer [{RuCl(μ-Cl)(η 6 -p-cymene)} 2 ], 14 guanidines ( i PrHN) 2 CNR (1a− e), 13 the lithium amidinate salt Li[( i PrN) 2 CMe], 25 and the allylic alcohols 1-(4-fluorophenyl)-2-propen-1-ol, 27 1-(4-chlorophenyl)-2propen-1-ol, 28 i Pr 2 (1e)). A solution of [{RuCl(μ-Cl)(η 6 -p-cymene)} 2 ] (0.306 g, 0.5 mmol) in 30 mL of toluene was treated with the appropriate guanidine 1a−e (2 mmol) at room temperature for 2 h. The gradual appearance of a white solid precipitate of the guanidinium chloride salts [( i PrHN) 2 C(NHR)][Cl] (3a−e) was observed.…”

Traceless Solid-Phase Organic Synthesis

“…Palladium-catalyzed cyclative cleavage of an allylic linkage was developed in a synthesis of 4-methylene pyrrolidines. , The key transformations in the synthesis of linear precursors 964 (Scheme ) were the Lewis acid-catalyzed imino-Sakurai reaction of immobilized allylsilane 962 with the in situ generated Boc-imine and the reductive alkylation of primary amine 963 . During the palladium-cyclative cleavage, authors assume the formation of an electrophilic π-allyl palladium species that are trapped by a nitrogen nucleophile to release the cyclic products .…”

Catalytic isomerization of allylic alcohols promoted by complexes [RuCl2(η6-arene)(PTA-Me)] under homogeneous conditions and supported on Montmorillonite K-10

“…Organic solvents were dried by standard methods and distilled under nitrogen before use. All reagents were obtained from commercial suppliers and used without further purification, with the exception of compounds PTA-Me (1) [21], [23], 1-(3-methoxyphenyl)-2-propen-1-ol (4i) [24], 1-(4-methoxyphenyl)-2-propen-1-ol (4j) [25], 1-(4-chlorophenyl)-2-propen-1-ol (4k) [26], 1-(4-fluorophenyl)-2-propen-1-ol (4l) [27], 1-(2-furyl)-2-propen-1-ol (4m) [26], (5R) -5,9-dimethyl-1,8-decadien-3-ol (4n) [18b] and (E/Z) -5,9-dimethyl-1,4,8-decatrien-3-ol (4o) [28], which were prepared by following the methods reported in the literature. Infrared spectra were recorded on a Perkin-Elmer 1720-XFT spectrometer.…”