Supporting Information

Visible light photoredox-catalyzed alkylation/ring expansion sequences of1-(1-arylvinyl)cyclobutanol derivatives

Su Jin Kwon, Yeon Joo Kim, and Dae Young Kim*Department of Chemistry, Soonchunhyang University, Asan, Chungnam 336-745, Korea

1.1 General information

All commercial reagents and solvents were used without purification. TLC analyses were carried out on pre-coated silica gel plates with F254 indicator. Visualization was accomplished by UV light (254 nm), I2, p-anisaldehyde, ninhydrin, and phosphomolybdic acid solution as an indicator. Purification of reaction products was carried out by flash chromatography using E. Merck silica gel 60 (230-400 mesh). 1H NMR,13C NMR, and 19F NMR spectra were recorded at 400 MHz, 100 MHz, 376 MHz respectively, on a Jeol ECS 400 MHz NMR spectrometer. Chemical shift values () are reported in ppm relative to Me4Si as the internal references and PhCF3 as the external references. Mass spectra were measured on Jeol HX110/110A using electrospray ionization technique.

1.2 Preparation of starting materials1-(1-Arylvinyl)cyclobutanol derivatives 1 were prepared in accordance with literature methods.1

2. General procedure for the visible-light-induced photocatalytic alkylation/1,2-carbon migration sequences for the synthesis of bis(alkoxycarbonyl)methyl-substituted cyclic ketones

An oven-dried Schlenk tube was equipped with a magnetic stir bar, trimethyl(1-(1-arylvinyl)cyclobutoxy)silane 1 (0.3 mmol), fac-Ir(ppy)3 (0.009 mmol), BrCH(CO2Et)2 (2, 0.6 mmol), 2,6-lutidine (0.6 mmol) and DMSO (5 mL). The mixture was degassed by the freeze-pump-thaw procedure. The reaction mixture was allowed to stir for 1 h under irradiation of blue LEDs (5 W). After the reaction was finished, the mixture was added ammonium chloride and extracted with ethyl acetate. The organic layers were dried over Na2SO4, concentrated in vacuum and purified by chromatography on silica gel (ethyl acetate:n-hexane = 1:20) to afford bis(alkoxycarbonyl)methyl-substituted cyclic ketones 3.

Diethyl 2-((2-oxo-1-phenylcyclopentyl)methyl)malonate (3a):

1H NMR (400 MHz, CDCl3) 7.39-7.31 (m, 4 H), 7.25-7.23 (m, 1 H), 4.17-4.04 (m, 2H), 3.98 (q, J = 7.2 Hz, 2 H), 3.17 (dd, J = 7.2 Hz, 6.0 Hz, 1 H), 2.68 (dd, J = 14.6 Hz, 6.0 Hz, 1H), 2.62-2.58 (m, 1H), 2.31-2.26 (m, 3H), 2.01-1.91 (m, 2H), 1.83-1.71 (m, 1H), 1.23 (t, J = 7.0 Hz, 3H), 1.16 (t, J = 7.0 Hz, 3H) ; 13C NMR (100 MHz, CDCl3) , 169.7, 169.1, 137.3, 128.7, 127.3, 127.2, 61.5, 61.4, 55.7, 48.6, 36.9, 36.8, 34.4, 18.5, 14.0, 13.9; R (film)

1727 cm-1; ESI-HRMS : m/z calcd for C19H25O5 [M+H]+ : 333.1702; found 333.1706.

Diethyl 2-((2-oxo-1-(p-tolyl)cyclopentyl)methyl)malonate (3b):

1H NMR (400 MHz, CDCl3) 7.25 (d, JHz, 2H), 7.13 (d, J= 8.4 Hz, 2H), 4.17-4.05 (m, 2H), 3.99 (q, J= 7.2 Hz, 2H), 3.15 (d, J= 8.0 Hz, 5.6 Hz, 1H), 2.66 (d, J= 14.6 Hz, 5.6 Hz, 1H), 2.61-2.55 (m, 1H), 2.31 (s, 3H), 2.29-2.23 (m, 3H), 1.98-1.87 (m, 2H), 1.82-1.72 (m, 1H), 1.23 (t, J= 7.2 Hz, 3H), 1.16 (t, J= 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) 218.4, 169.7, 169.2, 137.0, 134.0, 129.4, 127.2, 61.5, 61.4, 55.4, 48.6, 36.8, 36.7, 34.3, 20.9, 18.5, 14.0, 13.9; ESI-HRMS : m/z calcd for C20H27O5[M+H]+ : 347.1858; found 347.1856.

Diethyl 2-((1-(4-fluorophenyl)-2-oxocyclopentyl)methyl)malonate(3c):

1H NMR (400 MHz, CDCl3) 7.37-7.29 (m, 2 H), 7.05-6.99 (m, 2 H), 4.18-4.05 (m, 2H), 3.97 (q, J = 7.2 Hz, 2 H), 3.13 (dd, J = 7.2 Hz, 6.0 Hz, 1 H), 2.63 (dd, J = 14.8 Hz, 6.0 Hz, 1H), 2.57-2.50 (m, 1H), 2.29-2.22 (m, 3H), 2.02-1.92 (m, 2H), 1.81-1.70 (m, 1H), 1.21 (t, J = 7.0 Hz, 3H), 1.15 (t, J = 7.0 Hz, 3H) ; 13C NMR (100 MHz, CDCl3) , 169.6, 169.0, 162.0 (d, J = 245.0 Hz), 133.0, 129.1 (d, J = 8.6 Hz), 115. 5 (d, J = 20.9 Hz), 61.6, 61.5, 55.0, 48.5, 36.9, 36.8, 34.5, 18.4, 14.0, 13.9; 19F NMR (376 MHz, CDCl3) ESI-HRMS : m/z calcd for C19H24FO5 [M+H]+ : 351.1608; found 351.1604. Diethyl 2-((1-(4-chlorophenyl)-2-oxocyclopentyl)methyl)malonate(3d):

1H NMR (400 MHz, CDCl3) 7.34-7.29 (m, 4 H), 4.17-4.04 (m, 2H), 3.99 (q, J = 7.0 Hz, 2 H), 3.15 (t, J = 6.4 Hz, 1 H), 2.64 (dd, J = 14.6 Hz, 5.8 Hz, 1H), 2.55-2.51 (m, 1H), 2.31-2.24 (m, 3H), 2.01-1.93 (m, 2H), 1.82-1.76 (m, 1H), 1.23 (t, J = 7.0 Hz, 3H), 1.17 (t, J = 7.0 Hz, 3H) ; 13C NMR (100 MHz, CDCl3) , 169.5, 168.9, 136.0, 133.4, 128.8, 128.7, 61.6, 61.5, 55.1, 48.5, 36.9, 36.7, 34.4, 18.5, 13.9, 13.8; ESI-HRMS : m/z calcd for C19H24ClO5 [M+H]+ : 367.1312; found 367.1310. Diethyl 2-((2-oxo-1-(m-tolyl)cyclopentyl)methyl)malonate(3e):

1H NMR (400 MHz, CDCl3) 7.24-7.20 (m, 1 H), 7.16-7.15 (m, 2H), 7 4.17-4.04 (m, 2H), 7.06 (d, J = 7.6 Hz, 1H), 4.17-4.05 (m, 2H), 3.99 (q, J = 7.2 Hz, 2 H), 3.18 (dd, J = 8.0 Hz, 5.6 Hz, 1 H), 2.62-2.56 (m, 1H), 2.34 (s, 3H), 2.30-2.24 (m, 3H), 1.99-1.88 (m, 2H), 1.83-1.70 (m, 1H), 1.23 (t, J = 7.2 Hz, 3H), 1.17 (t, J = 7.2 Hz, 3H) ; 13C NMR (100 MHz, CDCl3) , 169.7, 169.2, 138.3, 137.2, 128.6, 128.1, 127.9, 124.2, 61.5, 61.4, 55.7, 48.6, 36.9, 36.7, 34.4, 21.6, 18.5, 14.0, 13.9; ESI-HRMS : m/z calcd for C20H27O5[M+H]+ : 347.1858; found 347.1860.

Diethyl 2-((1-(3-fluorophenyl)-2-oxocyclopentyl)methyl)malonate(3f):

1H NMR (400 MHz, CDCl3) 7.33-7.28 (m, 1 H), 7.17-7.10 (m, 2 H), 6.98-6.93 (m, 1H), 4.18-4.06 (m, 2H), 4.01 (q, J = 7.0 Hz, 2 H), 3.17 (dd, J = 7.2 Hz, 6.0 Hz, 1 H), 2.66 (dd, J = 14.6 Hz, 5.4 Hz, 1H), 2.55-2.51 (m, 1H), 2.32-2.26 (m, 3H), 2.03-1.95 (m, 2H), 1.84-1.73 (m, 1H), 1.24 (t, J = 7.0 Hz, 3H), 1.18 (t, J = 7.4 Hz, 3H) ; 13C NMR (100 MHz, CDCl3) , 169.5, 168.9, 163.0 (d, J = 245.1 Hz), 140.3 (d, J = 7.6 Hz), 130.2 (d, J = 7.7 Hz), 123.0 (d, J = 2.9 Hz), 114.5 (d, J = 22.0 Hz), 114.4 (d, J = 21.0 Hz), 61.6, 61.5, 55.4, 48.4, 37.0, 36.7, 34.6, 18.5, 13.9, 13.8; 19F NMR (376 MHz, CDCl3) ESI-HRMS : m/z calcd for C19H24FO5 [M+H]+ : 351.1608; found 351.1605. Diethyl 2-((1-(naphthalen-2-yl)-2-oxocyclopentyl)methyl)malonate (3g):

1H NMR (400 MHz, CDCl3) 8.22 (d, J = 8.4 Hz, 1H), 7.82 (dd, J = 34.0 Hz, 8.4 Hz, 2H), 7.53-7.45 (m, 2H), 7.39-7.32 (m, 2H), 4.11-4.05 (m, 2H), 3.90-3.78 (m, 2H), 3.49 (dd, J = 7.2 Hz, 4.8 Hz, 1H), 3.01 (dd, J = 15.0 Hz, 7.2 Hz, 1H), 2.97-2.91 (m, 1H), 2.81 (dd, J = 15.0 Hz, 4.8 Hz, 1H), 2.56-2.48 (m, 1H), 2.43-2.34 (m, 1H), 2.13-1.96 (m, 1H), 1.81-1.69 (m, 1H), 1.16 (t, J = 7.2 Hz, 3H), 1.08 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) 220.1, 169.6, 169.5, 135.2, 134.9, 130.9, 129.5, 128.9, 126.0, 125.7, 125.6, 125.4, 124.9, 61.5, 61.4, 57.2, 48.9, 37.0, 36.6, 33.8, 18.5, 13.9, 13.8;ESI-HRMS : m/z calcd for C23H27O5

[M+H]+ : 383.1858; found 383.1856. Dimethyl 2-((2-oxo-1-phenylcyclopentyl)methyl)malonate (3h):

1H NMR (400 MHz, CDCl3) 7.38-7.32 (m, 4 H), 7.27-7.23 (m, 1 H), 3.65 (s, 3 H), 3.54 (s, 3H), 3.24 (dd, J = 7.4 Hz, 5.6 Hz, 1 H), 2.69 (dd, J = 14.4 Hz, 5.6 Hz, 1H), 2.63-2.57 (m, 1H), 2.35-2.23 (m, 3H), 2.04-1.90 (m, 2H), 1.83-1.71 (m, 1H); 13C NMR (100 MHz, CDCl3) , 170.0, 168.5, 137.1, 128.8, 127.4, 127.2, 55.6, 52.6, 52.5, 48.2, 37.0, 36.9, 34.4, 18.5; ESI-HRMS : m/z calcd for C17H21O5 [M+H]+ : 305.1389; found 305.1391.

Diisopropyl 2-((2-oxo-1-phenylcyclopentyl)methyl)malonate (3i):

1H NMR (400 MHz, CDCl3) 7.39-7.31 (m, 4 H), 7.26-7.23 (m, 1 H), 4.97 (sep, J = 6.4 Hz, 1H), 4.83 (sep, J = 6.4 Hz, 1H), 3.08 (dd, J = 7.4 Hz, 5.6 Hz, 1H), 2.66 (dd, J = 14.8 Hz, 5.6 Hz, 1H), 2.61-2.57 (m, 1H), 2.30-2.25 (m, 3H), 2.01-1.91 (m, 2H), 1.83-1.71 (m, 1H), 1.21 (d, J = 6.4 Hz, 6H), 1.14 (t, J = 6.4 Hz, 6H); 13C NMR (100 MHz, CDCl3) , 169.3, 168.7, 137.5, 128.7, 127.3, 69.0, 55.7, 48.9, 37.0, 36.5, 34.4, 21.6, 21.5, 21.4, 18.5;ESI-HRMS : m/z calcd for C21H29O5 [M+H]+ : 361.2015; found 361.2017.

Diethyl 2-((1-benzyl-2-oxocyclopentyl)methyl)malonate (3j):

1H NMR (400 MHz, CDCl3) 7.28-7.20 (m, 3 H), 7.11-7.10 (m, 2 H), 4.21-4.15 (m, 6H), ), 3.15 (t, J = 6.4 Hz, 1 H), 2.87 (d, J = 14.0 Hz, 1 H), 2.63 (d, J = 14.0 Hz, 1H), 2.39-2.25 (m, 3H), 2.08-1.98 (m, 2H), 1.94-1.86 (m, 1H), 1.23 (t, J = 7.0 Hz, 3H), 1.25 (t, J = 7.2 Hz, 3H) ; 13C NMR (100 MHz, CDCl3) 217.7, 169.5, 168.9, 140.3, 130.1, 128.2, 61.5, 55.4, 48.4, 37.0, 36.6, 34.5, 29.9, 18.5, 13.9; ESI-HRMS : m/z calcd for C20H27O5 [M+H]+ : 347.1858; found 347.1861.

Ethyl 3-(2-oxo-1-phenylcyclopentyl)propanoate (5):

1H NMR (400 MHz, CDCl3) 7.39-7.32 (m, 4 H), 7.26-7.23 (m, 1 H), 4.04 (q, J = 7.2 Hz, 2H), 2.62-2.57 (m, 1H), 2.38-2.22 (m, 3H), 2.19-1.91 (m, 5H), 1.88-1.76 (m, 1H), 1.20 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) , 173.3, 138.5, 128.7, 127.1, 126.9, 60.4, 55.9, 37.5, 34.5, 33.5, 30.0, 18.6, 14.1;ESI-HRMS : m/z calcd for C16H21O5 [M+H]+ : 261.1491; found 261.1495. Diethyl 2-methyl-2-((2-oxo-1-phenylcyclopentyl)methyl)malonate (7):

1H NMR (400 MHz, CDCl3) m, 2H), 7.31 (t, J = 7.6 Hz, 2H), 7.24-7.21 (m, 1H), 4.14 (q, J = 7.2 Hz, 2H), 4.01 (dq, J = 10.8 Hz, 7.2 Hz, 1H), 3.89 (dq, J = 10.4 Hz, 7.2 Hz, 1H), 2.78 (d, J = 14.8 Hz, 1H), 2.68 (dd, J = 13.2 Hz, 6.0 Hz, 1H), 2.42 (d, J = 14.8 Hz,

1H), 2.23-2.18 (m, 2H), 2.06-1.89 (m, 2H), 1.73-1.62 (m, 1H), 1.23 (t, J = 7.2 Hz, 3H), 1.21 (s, 3H), 1.20 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) 218.2, 172.6, 171.8, 138.2, 128.6, 127.4, 127.1, 61.4, 61.2, 55.9, 52.9, 42.8, 35.9, 33.0, 21.4, 18.5, 13.9, 13.8; ESI-HRMS : m/z calcd for C20H27O5 [M+H]+ : 347.1858; found 347.1859.

Diethyl 2-(2-oxo-2',3'-dihydrospiro[cyclopentane-1,1'-inden]-2'-yl)malonate (9):

Major diastereomer : 1H NMR (400 MHz, CDCl3) 7.19-7.17 (m, 3 H), 7.03-7.01 (m, 1 H), 4.24 (m, 4H), 3.79 (d, J = 10.4 Hz, 1H), 3.27-3.16 (m, 2H), 2.83 (dd, J = 14.4 Hz, 4.6 Hz, 1H), 2.53-2.44 (m, 1H), 2.40-2.32 (m, 2H), 2.26-2.08 (m, 3H), 1.28 (t, J = 7.2 Hz, 3H), 1.25 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) , 169.3,168.8, 146.5, 141.6, 127.5, 127.2, 124.6, 123.0, 63.1, 61.5, 61.4, 52.7, 48.2, 39.0, 37.8, 36.0, 19.9, 14.1, 14.0; ESI-HRMS : m/z calcd for C20H25O5 [M+H]+ : 345.1702; found 345.1704.

3. Radical inhibition experiment

An oven-dried Schlenk flask was equipped with a magnetic stir bar, trimethyl(1-(phenyvinyl)cyclobutoxy)silane (1a, 0.3 mmol), fac-Ir(ppy)3 (0.009 mmol), ethyl bromomalonate (2a, 0.75 mmol), 2,6-lutidine (0.45 mmol), and 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO, 0.75 mmol). The flask was evacuated and backfilled with N2 for three times. And, 2 mL of DMSO was added with syringe under N2. The reaction mixture was stirred for 1 h under irradiation of blue LEDs (5 W, 455 nm). The reaction mixture was then diluted with ethyl acetate and washed with brine. The organic layers were dried over Na2SO4, concentrated in vacuum. The bis(ethoxycarbonyl)methyl-substituted cyclic ketone 3a was observed in trace amount in crude NMR and TLC analysis. TEMPO adduct 12 of the radical intermediate I was isolated in 35% yield after silica gel chromatography.

Diethyl 2-((2,2,6,6-tetramethylpiperidin-1-yl)oxy)malonate (12):

1H NMR (400 MHz, CDCl3) d 4.92 (s, 1 H), 4.31-4.18 (m, 4H), 1.40-1.55 (m, 6H), 1.29 (t, J = 7.2 Hz, 6H), 1.15 (s, 6H), 1.07(s, 6H); 13C NMR (100 MHz, CDCl3) d 167.3, 86.8, 61.6, 60.3, 40.1, 32.5, 20.1, 17.0, 14.0; ESI-HRMS : m/z calcd for C16H30NO5 [M+H]+ : 316.2124; found 316.2127.

4. References 1. (a) Shu, X. Z.; Zhang, M.; He, Y.; Frei H., Toste, F. D. J. Am. Chem. Soc. 2014, 136, 5844; (b) Woo, S. B.; Kim, D. Y. J. Fluorine Chem. 2015, 178, 214; (c) Suh, C. W.; Kim, D. Y. Tetrahedron Lett. 2015, 56, 5661. (d) Yin, Q.; You, S.-L. Org. Lett. 2014, 16, 1810.5. NMR spectra

Fluorine NMR