Imidazolinium and amidinium salts as Lewis acid organocatalysts

Abstract

SummaryThe application of imidazolinium and amidinium salts as soft Lewis acid organocatalysts is described. These salts were suitable catalysts for the activation of unsaturated thioesters in a Diels–Alder reaction and in the ring opening of thiiranes and epoxides. The products were isolated in good yields. The mild catalysts did not cause desulfurization of the products containing a thiol or thiocarbonyl group.

Synthesis of New Camphor-Based Carbene Ligands and Their Application in a Copper-Catalyzed Michael Addition with B2Pin2

“…1 H NMR spectra were acquired at r.t. on a Bruker Avance 500 (500 MHz) in deuterated solvents as stated. 13…”

“…1 H NMR (500 MHz, CDCl 3 ): δ = 8.95 (s, 1 H, H3), 8.52 (s, 1 H, H10′′), 8.25 (d, J = 8.9 Hz, 2 H, H5′′, H4′′), 8.03 (d, J = 8.5 Hz, 2 H, H8′′, H1′′), 7.96 (ddd, J = 4.9, 1.8, 0.7 Hz, 1 H, H6′), 7.88 (d, J = 8.4 Hz, 1 H, H3′), 7.78 (ddd, J = 8.4, 7.4, 1.9 Hz, 1 H, H4′), 7.64 (ddd, J = 8.9, 6.6, 1.3 Hz, 2 H, H7′′, H2′′), 7.53-7.47 (m, 2 H, H6′′, H3′′), 7.06 (ddd, J = 7.4, 4.9, 0.6 Hz, 1 H, H5′), 6.07 (dd, J = 51.9, 15.2 Hz, 2 H, H1′′′), 4.72 (d, J = 5.1 Hz, 1 H, H5), 2.68 (ddd, J = 14.5, 9.5, 4.7 Hz, 1 H, H7), 2.38 (ddt, J = 14.9, 12.1, 4.9 Hz, 1 H, H6), 2.22-2.09 (m, 1 H, H6), 2.09-1.99 (m, 1 H, H7), 1.64 (s, 3 H, H11), 1.28 (s, 3 H, H10), 1.15 (s, 3 H, H9). 13 C NMR (126 MHz, CDCl 3 ): δ = 150.6 (C3), 150.0 (C2′), 148.2 (C6′), 140.3 (C4′), 131.3 (C4′′a, C4′′b), 131.2 (C9′′a, C8′′a), 130.8 (C10′′), 129.8 (C8′′, C1′′), 128.3 (C7′′, C2′′), 125.6 (C6′′, C3′′), 122.7 (C5′), 122.5 (C5′′, C4′′), 121.4 (C9′′), 113.5 (C3′), 74.0 (C1), 65.7 (C5), 48.0 (C1′′′), 41.8 (C8), 40.2 (C7), 32.0 (C6), 21.9 (C10), 17.1 (C9), 14.9 (C11). 1,8,8-trimethyl-4-(pyridin-2-yl)-2,4-diazabicyclo[3.2.1]oct-2-en-2-ium Bromide 13Amidine 9 (617 mg, 2.69 mmol) and di(naphthalen-1-yl)methyl bromide 15 (1.03 g, 2.96 mmol) in MeCN (5 mL) were refluxed for 16 h. The solvent was removed and the salt was purified by column chromatography (CH 2 Cl 2 -MeOH, 9:1).…”

“…9g Recently, we reported the syntheses of C 1 symmetric salts of type 3 based on camphor via (+)-cis-1,2,2-trimethylcyclopentane-1,3-diamine (7), which can be prepared in one step from (+)-camphoric acid via the Schmidt reac-tion. 12 We applied these salts as weak Lewis acid catalysts, 13 and after deprotonation as Lewis base carbene organocatalyst in a Wynberg reaction giving the product in up to 92% ee. 14 Thereafter, the groups of Newman and Cavell reported the synthesis of several new pincer complexes like 4.…”

Towards Tartaric‐Acid‐Derived Asymmetric Organocatalysts

“…Chiral guanidine systems are another promising class of Lewis acidic (phase-transfer) catalysts 36–38. In 2002 Nagasawa et al reported the use of the tartaric-acid-derived C 2 -symmetric pentacyclic guanidine derivative 82 (Scheme 22) as a powerful chiral catalyst for the benchmark alkylation of Schiff base 56 36.…”

Influence of Ionic Liquids on an Iron(III) Catalyzed Three-Component Coupling/Hydroarylation/Dehydrogenation Tandem Reaction

“…Due to our interest in ionic liquids [ 4 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ], we wanted to explore the catalytic oxidative behavior of tetrachloroferrate-based ionic liquids in the synthesis of a quinoline derivate. Quinoline derivates and quinoline itself are important structural units in a variety of biologically active natural products.…”