Lewis acid-catalyzed Friedel–Crafts reactions toward highly versatile, α-quaternary oxime ethers

Abstract

The synthesis of all-carbon-substituted, quaternary stereocenters through Lewis acid-catalyzed Friedel-Crafts alkylation of cyclic and acyclic 2-hydroxy oxime ethers proceeds under mild reaction conditions and with high yields. Moreover, the oxime ether moiety can be easily manipulated into various functional groups through subsequent modifications.

Oxidative Rearrangement of Stilbenes to 2,2-Diaryl-2-hydroxyacetaldehydes

“…Purified by column chromatography (5% EtOAc in petroleum ether, R f = 0.5); yield: 75 mg (64%); colorless solid; mp: 64–66 °C (lit. 17 64–66 °C); IR(neat) ν max 3462, 2925, 1706, 1492, 1447, 1335, 1157, 1055, 754, 696 cm –1 ; cm –1 ; 1 H NMR (400 MHz, CDCl 3 ): δ 7.28 (s, 10H), 4.76 (s, 1H), 2.17 (s, 3H) ppm; 13 C NMR (100 MHz, CDCl 3 ): δ 208.7 (s), 141.4 (s, 2C), 128.5 (d, 4C), 128.3 (d, 4C), 128.1 (d, 2C), 85.8 (s), 26.3 (q) ppm; HRMS (ESI): calcd. for C 15 H 14 O 2 Na: 249.0886 [M + Na] + ; found: 249.0884.…”

“…Purified by column chromatography (5% EtOAc in petroleum ether, R f = 0.5); yield: 51 mg (45%); colorless solid; mp: 50−52 °C; IR(neat) ν max 3482,2951,1720,1509,1450,1338,1175,1014,829,793,741, 699 cm −1 ; 1 H NMR (400 MHz, CDCl 3 ): δ 9.88 (s, 1H), 7.31 (s, 5H), 7.18 (s, 4H), 4.28 (s, 1H), 2.84 (quin, J = 6.9 Hz, 1H), 1.17 (d, J = 6.9 Hz, 6H) ppm; 13 2-Chloro-2-(4-chlorophenyl)-2-phenylacetaldehyde (2e). 17 Purified by column chromatography (5% EtOAc in petroleum ether, R f = 0.5); yield: 55 mg (45%); yellow syrup; IR(neat) ν max 3466,2922,1720,1490,1400,1092,1011,823,823,792,758, 698 cm −1 ; 1 H NMR (400 MHz, CDCl 3 ): δ 9.96 (s, 1H), 7.28−7.55 (m, 9H), 4.41 (s, 1H) ppm; 13 C NMR (100 MHz, CDCl 3 ): δ 197.5 (d), 139.0 (s), 137.7 (s), 134.6 (s), 129.0 (d, 2C), 128.9 (d, 2C), 128.8 (d) 2-(4-Bromophenyl)-2-hydroxy-2-phenylacetaldehyde (2f). Purified by column chromatography (5% EtOAc in petroleum ether, R f = 0.5); yield: 55 mg (49%); colorless syrup; IR(neat) ν max 3451,2922,1720,1487,1448,1395,1153,1072,1006,898,817,791,756,697, 653 cm −1 ; 1 H NMR (500 MHz, CDCl 3 ): δ 9.98 (s, 1H), 7.57 (d,J = 8.4 Hz,2H),3H),2H), 7.30 (d, J = 8.4 Hz, 2H), 4.41 (s, 1H) ppm; 13 C NMR (125 MHz, CDCl 3 ): δ 197.5…”

Relation Between Coordination and Lewis‐Acid Property of MOF‐Derived Mononuclear Zn(II) Catalyst Toward Epoxide Hydroxylation

“…Zn 2 + salts, considered to be borderline Lewis-acids in Pearson's HSAB classification, [37] is attractive in diversified Lewis-acid-mediated transformations. Thereby, the series of ZnÀ N/PÀ C samples are firstly evaluated by Friedel-Crafts acylation reaction, [38] which has been considered as a classic Lewis-acid catalysis to form diversified arylketones that useful in pharmaceuticals and agrochemicals. The TOF values varied from 18.1 to 48.1 h À 1 follows the sequence of ZIF-8-P-900 > ZIF-8-P-800 > ZIF-8-P-700 > ZIF-8-D-700 > ZIF-8-700 (see Table S4).…”

Rapid, One-Step Synthesis of α-Ketoacetals via Electrophilic Etherification

“…The following was drafted from known procedures. − A solution of α-hydroxy acetal ( 44 , 45 , 46 , or 47 , 1.00 equiv, n mmol) in acetone ( V = 15 mL) was mixed with 10% aq. hydrochloric acid (1 mL) and equipped with a reflux condenser/hot plate apparatus.…”