, Ethyl 4-methylenechromane-2-carboxylate (1a)

, Colorless oil, 172 mg, 79%; 1 H NMR (300 MHz, Chloroform-d, ? ppm) 7.53 (dd, J = 7.9, 1.6 Hz, 1H), vol.7

. Hz,

. Hz,

, Ethyl 7-fluoro-4-methylenechromane-2-carboxylate (1b)

, Colorless oil, 156 mg, 66%; 1 H NMR (300 MHz, Chloroform-d, ? ppm) 7.47 (dd, J = 8.7, 6.4 Hz, 1H), 6.71-6.60 (m, 2H), 5.47-5.44 (m, 1H), vol.154

, Ethyl 7-methoxy-4-methylenechromane-2-carboxylate (1c)

, Colorless oil, 198 mg, 80 % (mixture 1c and 10c)

H. Nmr,

C. Mhz,

, Ethyl 7-methoxy-6-methyl-4-methylenechromane-2

, 47 (s, 1H), 5.38 (s, 1H), Colorless oil, 152 mg, 58%; 1 H NMR (400 MHz, Chloroform-d, ? ppm) 7.27 (s, 1H), vol.6

. Hz, 1H)), 2.14 (s, 3H), 1.28 (t, J = 7.1 Hz, 3H), vol.13, p.101

C. Mhz,

, Ethyl 6-chloro-4-methylenechromane-2-carboxylate. (1f)

, Colorless oil, 192 mg, 76%; 1 H NMR (400 MHz, Chloroform-d) ? 7.48 (d, J = 2.5 Hz, 1H), 7.15 (dd, J = 8.8, 2.5 Hz, 1H), vol.6

, Ethyl 8-fluoro-4-methylenechromane-2-carboxylate. (1g)

, Colorless oil, 208 mg, 88%; 1 H NMR (300 MHz

. Hz,

, Ethyl 6-methyl-4-methylenechromane-2-carboxylate (1h)

, Colorless oil, 179 mg, 77%; 1 H NMR (400 MHz, Chloroform-d, ? ppm) 7.33 (dd, J = 2.0, 0.9 Hz, 1H), 7.01 (dd, J = 8.4, 2.1 Hz, 1H), 6.88 (d, J = 8.3 Hz, 1H), 5.55-5.53 (m, 1H)

, Colorless oil, 21 mg, 95 %; 1 H NMR (400 MHz, Chloroform-d, ? ppm) 7.22-7.12 (m, 2H), 6.96-6.88 (m, 2H), 5.65-5.60 (m, 1H), 5.35-5.29 (m, 1H), 4.29-4.14 (m, 2H), 2.05 (t, J = 1.6 Hz, 3H), 1.27 (t, J = 7.1 Hz, 3H). 13 C NMR (101 MHz

, Ethyl 7-fluoro-4-methyl-2H-chromene-2-carboxylate (10b)

, Chloroform-d) ? 7.13 (dd, J = 8.2, 6.3 Hz, 1H), 6.74-6.58 (m, 2H), 5.58 (dt, Colorless oil, 22 mg, 94 %; 1 H NMR (300 MHz, p.75

. Mhz, CDCl3) ? 169.8, 163.3 (d, J = 247.2 Hz), 154.2 (d, J =, vol.12, issue.3

. Hz, , vol.124

. Hz, 103.8 (d, J = 25.3 Hz)

. Mhz, Chloroform-d, ? ppm) -111.1. HRMS (ESI + ) calculated for

, Ethyl 7-methoxy-4-methyl-2H-chromene-2-carboxylate (10c)

, Colorless oil, 24 mg, 96 %; 1 H NMR (300 MHz, Chloroform-d)

. Hz,

. Hz, 81 (s, 3H), 2.04 (t, J = 1.5 Hz, 3H), 1.30 (t, J = 7.1 Hz, 3H). 13 C NMR (101 MHz, CDCl3), vol.3

, Chloroform-d, ? ppm) 6.92 (s, 1H), 6.52 (s, 1H), 5.48 (dt, Colorless oil, 23 mg, 88 %; RMN 1 H (400 MHz

, Hydrogenation of ethyl 4-methylenechromane-2-carboxylate (1a): access to ethyl 4-methylchromane-2-carboxylate (11a)

, A solution of compound 1a (22 mg, 0.1 mmol) in methanol (5 mL) was stirred under hydrogen (1 atm.) in the presence of 5%

/. Pd, , vol.1

, Colorless oil, 20 mg, 92 %; major isomer: 1 H NMR (400 MHz, Chloroform-d, ? ppm) 7.23 (d, J = 7.7 Hz, 1H), vol.7

. Hz,

, Hz, 1H), 1.85 (dt, J = 13.5, 11.0 Hz, 1H), 1.38 (d, 6.8 Hz, 3H), 1.35 (t, J = 7.1 Hz, 3H). 13 C NMR (75 MHz

, Cu(OAc)2 (145 mg, 0.8 mmol) were added to the pinacol boronate 7a (173 mg, 0.8 mmol) in MeOH (5 mL). The solution was stirred vigorously at reflux for 5 hours. The mixture was concentrated and then extracted with dichloromethane. After evaporation of the solvent, the residue was purified by chromatography on silica gel, NaN3 (107 mg, 1.6 mmol) and

, Colorless oil, 73 mg, 55%; 1 H NMR (300 MHz

, Hz, 1H), 7.18-7.02 (m, 2H), 5.34 (q, J = 1.3 Hz, 1H), 5.14 (d, J = 1.7 Hz, 1H)

, A mixture of 12a (94 mg, 0.36 mmol) and triphenylphosphine (94 mg, 0.36 mmol) in THF (2 mL) was heated at 60°C for 6h

, White solid, 160 mg, 90%; 1 H NMR (300 MHz, Chloroform-d, ? ppm) ? 7.80-7.70 (m, 6H), 7.56-7.41 (m, 9H), vol.7

. Hz,

, Hz, 1H), 2.92 (ddd, J = 13.4, 9.4, 0.7 Hz, 1H), 1.16 (t, J = 7.1 Hz, 3H). 13 C NMR (75 MHz Chloroform-d

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