V. Hajzer, P. Alexy, A. Latika, J. Durmis, R. Šebesta

Supplementary material for

Optimization of stereoselective Michael addition of 2-(pentan-3-yloxy)acetaldehyde to N-[(Z)-2-nitroethenyl]acetamide with the aid of design of experiment

V. Hajzer, P. Alexy, A. Latika, J. Durmis, R. Šebesta

Contents

Experimental procedures

General

General procedure for the Michael addition

Derivatization of the Michael product for sample preparation for chiral HPLC

Pictures of NMR spectra

N-[(2R,3S)-1-nitro-4-oxo-3-(pentan-3-yloxy)butan-2-yl]acetamide (syn-3)

N-[(2R,3R)-1-nitro-4-oxo-3-(pentan-3-yloxy)butan-2-yl]acetamide (anti-3)

N-[(2R,3R)-4-[(9Z)-9H-fluoren-9-ylidene]-1-nitro-3-(pentan-3-yloxy)butan-2-yl]acetamide (syn)

N-[(2R,3S)-4-[(9Z)-9H-fluoren-9-ylidene]-1-nitro-3-(pentan-3-yloxy)butan-2-yl]acetamide (anti)

HPLC chromatograms

Additional data for DoE

Experimental procedures

General

NMR spectra were recorded on Varian NMR System 300 instrument (300 MHz for 1H, 75 MHz for 13C). Chemical shifts (δ) are given in ppm relative to tetramethylsilane or residual peak of solvent. Flash chromatography was performed on Across silica gel 60A, 0.035 – 0.070 nm. Thin-layer chromatography was performed on Merck TLC-plates silica gel 60, F-254 and preparative layer chromatography – Merck PLC-platessilicagel 60, F254, 2 mm. Enantiomeric excesses were determined by chiral HPLC on Chiralcel OD-H (Daicel Chemical Industries) column using hexane/i-PrOH as a mobile phase and UV detection. MS analyses were performed on LC-IT-TOF MS (Shimadzu, Kyoto, Japan) using Ascentis C18 column with gradient H2O/acetonitril elution over 33 min.

General procedure for the Michael addition

N-[(Z)-2-nitroethenyl]acetamide (32.5 mg, 0.25 mmol) was dissolved in CDCl3. The resulting solution was cooled in an ice-bath and 2-(pentan-3-yloxy)acetaldehyde (1, freshly distilled, 50 mg, 0.38 mmol, 50µL), aqueous solution of ClCH2CO2H (4.73 mg, 0.05 mmol) a(S)-C1 (8.14 mg, 0.025 mmol) dissolved in CDCl3 were added. The reaction mixture was stirred for 4h at 0°C (ice-bath). From this mixture, an aliquot sample (0.6 mL) was taken for NMR analysis and another portion was used for HPLC analysis (description below).

N-[(2R,3S)-1-nitro-4-oxo-3-(pentan-3-yloxy)butan-2-yl]acetamide

syn-3: 1H NMR, (300 MHz, CDCl3) δ 9.65 (t, J = 0.6 Hz, 1H), 6.10 (bd, J = 8.8 Hz, 1H), 5.16–4.98 (m, 1H), 4.59 (d, J = 6.6 Hz, 2H), 4.10 (d, J = 3.3 Hz, 1H), 3.45–3.38 (m, 1H), 1.99 (s, 3H), 1.67–1.48 (m, 4H), 0.98–0.87 (m, 6H); MS m/z [M+H]+ calculated for C11H21N2O5: 261.15, found: 261.13.

N-[(2S,3S)-1-nitro-4-oxo-3-(pentan-3-yloxy)butan-2-yl]acetamide

anti-3: 1H NMR, (300 MHz, CDCl3) δ 9.61 (d, J = 3.1 Hz, 1H), 6.51 (bd, J = 8.1 Hz,1H), 4.88–4.67 (m, 2H), 4.66–4.49 (m, 1H), 3.98–3.91 (m,1H), 3.33–3.23 (m, 1H), 2.00 (s, 3H), 1.67–1.38 (m, 4H), 1.02–0.73 (m, 6H). MS m/z [M+H]+ calculated for C11H21N2O5: 261.15, found: 261.13.

Derivatization of the Michael product for sample preparation for chiral HPLC

Into the crude reaction mixture from the Michael addition (0.077 mL) containing N-1-nitro-4-oxo-3-(pentan-3-yloxy)butan-2-yl]acetamide (3, 5 mg) 9H-fluoren-9-ylidentrifenyl-λ5-phoshane (10 mg) was added intoluene (0.5 mL). The resulting mixture was stirred for 1 h at 100°C. After cooling to r.t., 0.25 mL of this mixture was purified by preparative TLC (SiO2, hexane/EtOAc 2:1, detected by UV at 254 nm). Detected region of the plate was washed with hexane/propan-2-ol 4:1 giving a sample for HPLC analysis.

HPLC (Daicel OD-H column, hexane/propan-2-ol 85:15, 0.75 mL/min, 259 nm) tR (syn-isomer): 27.04 min and16.59 min; tR (anti-isomer): 13.14 min and10.56 min.

N-[(2S,3S)-4-(9H-fluoren-9-ylidene)-1-nitro-3-(pentan-3-yloxy)butan-2-yl]acetamide

1H NMR, (300 MHz, CDCl3) δ 7.79–7.61 (m, 4 H), 7.45–7.27 (m, 4 H), 6.42 (d, J = 9.3 Hz, 1H), 5.97 (bd, J = 8.7 Hz, 1H), 5.46 (dd, J = 4.1, 9.4 Hz, 1H), 4.96– 4.83 (m,1H), 4.83 – 4.66 (m, 2 H), 3.43 – 3.30 (m, 1H), 1.94 (s, 3H), 1.56–1.42 (m, 4 H), 0.91–0.86 (m, 6H). MS: m/z [M+Na+] calculated for: [C24H28N2O4Na] = 431.19, found: 431.18.

Pictures of NMR spectra

N-[(2R,3S)-1-nitro-4-oxo-3-(pentan-3-yloxy)butan-2-yl]acetamide(syn-3)

N-[(2R,3R)-1-nitro-4-oxo-3-(pentan-3-yloxy)butan-2-yl]acetamide(anti-3)

N-[(2R,3R)-4-[(9Z)-9H-fluoren-9-ylidene]-1-nitro-3-(pentan-3-yloxy)butan-2-yl]acetamide (syn)

N-[(2R,3S)-4-[(9Z)-9H-fluoren-9-ylidene]-1-nitro-3-(pentan-3-yloxy)butan-2-yl]acetamide (anti)

HPLC chromatograms

Additional data for DoE

Table S1. Factor levels for each designed experiment in the preliminary DoE.

No. / Order / Coding of factor levels
X1 / X2 / X3 / X4 / X5 / X6 / X7
1 / 1 / -1 / -1 / -1 / -1 / 1 / 1 / 1
2 / 3 / 1 / -1 / -1 / 1 / -1 / -1 / 1
3 / 5 / -1 / 1 / -1 / 1 / -1 / 1 / -1
4 / 7 / 1 / 1 / -1 / -1 / 1 / -1 / -1
5 / 9 / -1 / -1 / 1 / 1 / 1 / -1 / -1
6 / 12 / 1 / -1 / 1 / -1 / -1 / 1 / -1
7 / 10 / -1 / 1 / 1 / -1 / -1 / -1 / 1
8 / 13 / 1 / 1 / 1 / 1 / 1 / 1 / 1
9 / 2 / 0 / 0 / 0 / 0 / 0 / 0 / 0
10 / 4 / 0 / 0 / 0 / 0 / 0 / 0 / 0
11 / 6 / 0 / 0 / 0 / 0 / 0 / 0 / 0
12 / 8 / 0 / 0 / 0 / 0 / 0 / 0 / 0
13 / 11 / 0 / 0 / 0 / 0 / 0 / 0 / 0

Table S2. Factor levels for each experiments in the second run of DoE.

Coding of factor levels
No. / Order / X1 / X2 / X3 / X4 / X5
1 / 1 / -1 / -1 / -1 / -1 / 1
2 / 4 / 1 / -1 / -1 / -1 / -1
3 / 6 / -1 / 1 / -1 / -1 / -1
4 / 9 / 1 / 1 / -1 / -1 / 1
5 / 11 / -1 / -1 / 1 / -1 / -1
6 / 14 / 1 / -1 / 1 / -1 / 1
7 / 18 / -1 / 1 / 1 / -1 / 1
8 / 21 / 1 / 1 / 1 / -1 / -1
9 / 25 / -1 / -1 / -1 / 1 / -1
10 / 28 / 1 / -1 / -1 / 1 / 1
11 / 15 / -1 / 1 / -1 / 1 / 1
12 / 19 / 1 / 1 / -1 / 1 / -1
13 / 22 / -1 / -1 / 1 / 1 / 1
14 / 26 / 1 / -1 / 1 / 1 / -1
15 / 30 / -1 / 1 / 1 / 1 / -1
16 / 32 / 1 / 1 / 1 / 1 / 1
17 / 2 / -2 / 0 / 0 / 0 / 0
18 / 5 / 2 / 0 / 0 / 0 / 0
19 / 7 / 0 / -2 / 0 / 0 / 0
20 / 10 / 0 / 2 / 0 / 0 / 0
21 / 12 / 0 / 0 / -2 / 0 / 0
22 / 16 / 0 / 0 / 2 / 0 / 0
23 / 20 / 0 / 0 / 0 / -2 / 0
24 / 23 / 0 / 0 / 0 / 2 / 0
25 / 27 / 0 / 0 / 0 / 0 / -2
26 / 29 / 0 / 0 / 0 / 0 / 2
27a / 3 / 0 / 0 / 0 / 0 / 0
28a / 8 / 0 / 0 / 0 / 0 / 0
29a / 13 / 0 / 0 / 0 / 0 / 0
30a / 17 / 0 / 0 / 0 / 0 / 0
31a / 24 / 0 / 0 / 0 / 0 / 0
32a / 31 / 0 / 0 / 0 / 0 / 0
a Experiments performed at different times with identical reaction parameters for determination of experimental errors.

Table S3: Amounts of reagents for experiments resulting from the preliminary DoE.

No. / Order / …
X1 [mmol] / X2 [°C] / X3 [h] / X4 [ml] / X5 [mmol] / X6 [mmol] / X7 [mmol/ml] *
1 / 1 / 0.088 / -10 / 0.5 / 2.1 / 0.003 / 0.125 / 0.25
2 / 3 / 0.013 / -10 / 0.5 / 0.1 / 0.25 / 1.25 / 0.25
3 / 5 / 0.013 / +10 / 0.5 / 2.1 / 0.003 / 1.25 / 0.08
4 / 7 / 0.088 / +10 / 0.5 / 0.1 / 0.25 / 0.125 / 0.08
5 / 9 / 0.013 / -10 / 14.5 / 2.1 / 0.25 / 0.125 / 0.08
6 / 12 / 0.088 / -10 / 14.5 / 0.1 / 0.003 / 1.25 / 0.08
7 / 10 / 0.013 / +10 / 14.5 / 0.1 / 0.003 / 0.125 / 0.25
8 / 13 / 0.088 / +10 / 14.5 / 2.1 / 0.25 / 1.25 / 0.25
9 / 2 / 0.05 / 0 / 7.5 / 1 / 0.128 / 0.688 / 0.17
10 / 4 / 0.05 / 0 / 7.5 / 1 / 0.128 / 0.688 / 0.17
11 / 6 / 0.05 / 0 / 7.5 / 1 / 0.128 / 0.688 / 0.17
12 / 8 / 0.05 / 0 / 7.5 / 1 / 0.128 / 0.688 / 0.17
13 / 11 / 0.05 / 0 / 7.5 / 1 / 0.128 / 0.688 / 0.17

*Amount of nitroalkene was same in each experiment (32.5 mg, 0.25 mmol, 1eq.)

Table S4: Amounts of reagents for experiments resulting from the main DoE.

No. / Order / …
X1 [mmol] / X2 [ml] / X3 [mmol] / X4 [mmol] / X5 [ml] *
1 / 1 / 0.031 / 0.27 / 0.031 / 0.292 / 0.66
2 / 4 / 0.068 / 0.27 / 0.031 / 0.292 / 1.50
3 / 6 / 0.031 / 0.75 / 0.031 / 0.292 / 1.30
4 / 9 / 0.068 / 0.75 / 0.031 / 0.929 / 0.75
5 / 11 / 0.307 / 0.27 / 0.068 / 0.292 / 1.40
6 / 14 / 0.068 / 0.27 / 0.068 / 0.292 / 0.80
7 / 18 / 0.031 / 0.75 / 0.068 / 0.292 / 0.70
8 / 21 / 0.068 / 0.75 / 0.068 / 0.292 / 1.60
9 / 25 / 0.031 / 0.27 / 0.031 / 0.446 / 1.60
10 / 28 / 0.068 / 0.27 / 0.031 / 0.446 / 0.90
11 / 15 / 0.031 / 0.75 / 0.031 / 0.446 / 0.80
12 / 19 / 0.068 / 0.75 / 0.031 / 0.446 / 1.80
13 / 22 / 0.031 / 0.27 / 0.068 / 0.446 / 0.85
14 / 26 / 0.068 / 0.27 / 0.068 / 0.446 / 1.90
15 / 30 / 0.031 / 0.75 / 0.068 / 0.446 / 1.70
16 / 32 / 0.068 / 0.75 / 0.068 / 0.446 / 0.90
17 / 2 / 0.012 / 0.50 / 0.049 / 0.369 / 0.94
18 / 5 / 0.086 / 0.50 / 0.049 / 0.369 / 1.20
19 / 7 / 0.049 / 0.03 / 0.049 / 0.369 / 1.10
20 / 10 / 0.049 / 0.98 / 0.049 / 0.369 / 1.10
21 / 12 / 0.049 / 0.50 / 0.012 / 0.369 / 1.00
22 / 16 / 0.049 / 0.50 / 0.086 / 0.369 / 1.10
23 / 20 / 0.049 / 0.50 / 0.049 / 0.223 / 0.90
24 / 23 / 0.049 / 0.50 / 0.049 / 0.515 / 1.30
25 / 27 / 0.049 / 0.50 / 0.049 / 0.369 / 3.20
26 / 29 / 0.049 / 0.50 / 0.049 / 0.369 / 0.60
27 / 3 / 0.049 / 0.50 / 0.049 / 0.369 / 1.10
28 / 8 / 0.049 / 0.50 / 0.049 / 0.369 / 1.10
29 / 13 / 0.049 / 0.50 / 0.049 / 0.369 / 1.10
30 / 17 / 0.049 / 0.50 / 0.049 / 0.369 / 1.10
31 / 24 / 0.049 / 0.50 / 0.049 / 0.369 / 1.10
32 / 31 / 0.049 / 0.50 / 0.049 / 0.369 / 1.10

*X5 = volumeof CHCl3(CDCl3)

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