Chemo- and stereoselectivity in titanium-mediated regioselective ring-opening reaction of epoxides at the more substituted carbon

[1,2]-Wittig Rearrangement of (Benzyloxy)acetamides

“…18 Compound 6f was transformed into the corresponding monosilylated ether 7f, as this latter product was described in the literature. 19 By comparison of the NMR data of 6a and 7f with those described in the literature, the syn relative stereochemistry between the hydroxy and alkyl groups was attributed. 19,20 Similarities between the different hydroxyamides 4 were observed by analysis of the 1 H NMR data in term of chemical shift, 21 and coupling constants between the benzylic proton and the proton at the a-position of the amide (major diastereomer 3 J = 4.6-6.4 Hz, minor diastereomer 3 J = 3.1-4.7 Hz, with 3 J major > 3 J minor ).…”

“…19 By comparison of the NMR data of 6a and 7f with those described in the literature, the syn relative stereochemistry between the hydroxy and alkyl groups was attributed. 19,20 Similarities between the different hydroxyamides 4 were observed by analysis of the 1 H NMR data in term of chemical shift, 21 and coupling constants between the benzylic proton and the proton at the a-position of the amide (major diastereomer 3 J = 4.6-6.4 Hz, minor diastereomer 3 J = 3.1-4.7 Hz, with 3 J major > 3 J minor ). 22 On the basis of the chemical correlations obtained for compounds 6a and 7f, as well as the 1 H NMR observations, a syn stereochemistry for all the major isomers coming from the [1,2]-Wittig rearrangement, was assigned by analogy.…”

Electronic and chelation effects on the unusual C2‐methylation of N‐(para‐substituted)phenylaziridines with lithium organocuprates

“…It is well known that the ring‐opening reactions of most three‐membered heterocycles (e.g., oxiranes, aziridines, and thiiranes) usually lead to both the more hindered C2 opening ( minor ) and the less hindered C3 opening ( major ). The regioselective C2‐opening reactions have been achieved depending on the following conditions: C2 aromatic activations,9–11 heteroatom activations (e.g., N‐activating groups or aziridinium salts),12–15 catalysts (e.g., Lewis acids, metal–ligand complexes, metal oxides, and organic/inorganic catalysts),16–32 unique nucleophiles,33–38 and C2‐driecting effects of nucleophiles 39–42. Despite previous theoretical studies on the ring‐opening mechanism,43–56 little have been explored in regard to the favored opening at the more‐hindered C2 atom,57–61 especially at the benzylic C2 atom 62, 63.…”

A Non-Heme Iron(III) Complex with Porphyrin-like Properties That Catalyzes Asymmetric Epoxidation

“…trans-(3-(4-chlorophenyl)oxiran-2-yl)methyl benzoate (3k) White solid (61%, 71% ee); [α]20 D -39.5 (c 0.37, CHCl 3 ); mp 68-69 ºC; Rf = 0.48 (hexane/ethyl acetate = 4/1); 1 H NMR (500 MHz, CDCl 3 )  8.09 (2H, d, J = 8.9 Hz), 7.60-7.58 (1H, m), 7.46 (2H, dd, J = 8.9, 8.9 Hz), 7.33 (2H, d, J = 8.9 Hz), 7.26-7.23 (2H, m), 4.73 (1H, dd, J = 12.4, 3.5 Hz), 4.36 (1H, dd, J = 12.4, 5.9 Hz), 3.88 (1H, d, J = 2.5 Hz), 3.36-3.34 (1H, m); 13 C NMR (125 MHz, CDCl 3 )  166.2, 134.8, 134.3, 133.3, 129.8, 129.5, 128.8, 128.5, 127.0, 64.4, 59.5, 55.9; IR (neat)  max 2925, 1721, 1493, 1451, 1272, 1109, 1092, 824, 711 cm -1 ; HRMS (Fab) (m/z) [M+Na] + calculated for C 16 H 13 ClO 3 Na 311.0451, found: 311.0453 ( = +0.7 ppm) ; ee was determined by HPLC analysis (254 nm): Daicel Chiralpac AD-H 0.46 cm  × 25 cm (hexane/isopropyl alcohol=19/1, flow rate = 0.5 mL/min), retention time: 23.6 min (major), 21.8 min (minor). trans-(3-Naphthyloxiran-2-yl)methyl benzoate (3l) O Ph O O White solid (42%, 82% ee); [α] 20 D +35.3 (c 0.19, CHCl 3 ); mp 65-66 ºC; Rf = 0.50 (hexane/ethyl acetate = 4/1); 1 H NMR (500 MHz, CDCl 3 )  8.14-8.09 (3H, m), 7.89-7.87 (1H, m), 7.81 (1H, d, J = 8.0 Hz), 7.61-7.58 (1H, m), 7.53-7.44 (6H, m), 4.80 (1H, dd, J = 11.9, 4.0 Hz), 4.61 (1H, dd, J = 11.9, 5.9 Hz), 4.53 (1H, d, J = 1.5 Hz), 3.39-3.37 (1H, m); 13 C NMR (125 MHz, CDCl 3 )  166.3, 133.3, 133.2, 132.3, 131.2, 129.8, 129.6, 128.7, 128.5, 128.4, 126.5, 126.0, 125.5, 122.7, 122.4, 64.7, 58.5, 55.1; IR (neat)  max 1719, 1451, 1271, 1110, 800, 778, 710 cm -1 ; HRMS (Fab) (m/z) [M+H] + calculated for C 20 H 17 O 3 : 305.1178, found: 305.1182 ( = +1.3 ppm) ; ee was determined by HPLC analysis (254 nm): Daicel Chiralpac AD-H 0.46 cm  × 25 cm (hexane/isopropyl alcohol = 19/1, flow rate = 0.5 mL/min), retention time: 26.0 min (major), 22.9 min (minor).trans-(2S, 3S)-2-(methoxymethoxy)methyl-3-phenyloxirane (3m) 16S18 .3 (c 0.67, CHCl 3 ) ((2S, 3S)-form: lit 16. [α] 26 D -39.9 (c 1.00, CHCl 3 , >99% ee)); Rf = 0.40 (hexane/ethyl acetate=4/1);1 H NMR (500 MHz, CDCl 3 )  7.35-7.26 (m, 5H), 4.71 (1H, d, J =6.4 Hz), 4.69 (1H, d, J = 6.4 Hz), 3.88 (1H, dd, J = 11.9, 3.5 Hz), 3.81 (1H, d, J = 2.0 Hz), 3.71 (1H, dd, 11.9, 5.0 Hz), 3.39 (3H, s), 3.25-3.23 (1H, m); 13 C NMR (125 MHz, CDCl 3 )  136.8, 128.5, 128.3, 125.7, 96.7, 67.3, 60.9, 56.1, 55.4; IR (neat)  max 2932, 1498, 1463, 1214, 1153, 1135, 1108, 1037, 917, 880, 751, 698 cm -1 ; ee was determined by HPLC analysis (254 nm): Daicel Chiralpac AD-H 0.46 cm  × 25 cm (hexane/isopropyl alcohol = 19/1, flow rate = 0.5 mL/min), retention time: 19.7 min (major), 14.3 min (minor).…”