Carbamic acid, N-[2-(tributylstannyl)phenyl]-, 1,1-dimethylethyl ester synthesis

Yield:148493-54-3 80%

Reaction Conditions:

Stage #1: tert-butyl phenylcarbamatewith n-butyllithium in diethyl ether;pentane at -40 - 0; for 3.5 h;Inert atmosphere;
Stage #2: tributyltin chloride in diethyl ether;pentane at -78 - 0; for 6 h;Inert atmosphere;

Steps:

N-Boc-aniline (5.00 g, 25.9 mmol, 1.0 equiv) was placed in an oven dried 250 mL round bottomed-flask and dissolved in 52 mL of dry Et2O. The solution was cooled to -40 °C under an Ar atmosphere. t-BuLi (1.6 M in pentane, 34.0 mL, 54.4 mmol, 2.1 equiv) was added via a syringe pump over 30 min, during which the mixture became homogenous, and the resulting solution was stirred at 0 °C for 3 h. The reaction mixture was further cooled to -78 °C, treated with Bu3SnCl (6.8 mL, 25.1 mmol, 1.0 equiv), and stirred at 0 °C for 6 h. The reaction mixture was quenched with saturated aqueous NaHCO3 solution (50 mL) at 0 °C. The organics were extracted with Et2O (300 mL x 2) and washed with brine (50 mL). The combined organic layers were dried over Na2SO4 and concentrated under reduced pressure. Column chromatography using neutral alumina (Brockman activity 1, dry packed and pre-washed with a 40:4:1 mixture of Hex/Et3N/EtOAc, eluted with 20:1 mixture of Hex/EtOAc) gave 2c1b (10.0 g, 80%) as a colorless oil. 1H NMR (500 MHz, CDCl3): δ 7.70 (br s, 1H), 7.34 (dd, J = 7.5, 1.5, 1H), 7.32 (ddd, J = 7.5, 7.0, 1.5, 1H), 7.07 (ddd, J = 7.5, 6.5, 1.0, 1H), 6.30 (br s, 1H), 1.52 (nfom, 6H), 1.51 (s, 9H), 1.34 (sext, J = 7.5, 6H), 1.10 (nfom, 6H), and 0.89 (t, J = 7.5, 9H); 13C NMR (CDCl3, 75 MHz) δ 153.5, 143.6, 137.0, 129.3, 124.2, 122.0 (br), 80.3, 29.1, 28.5, 27.4, 13.7, and 10.1; IR (thin film): 3440, 2956, 2926, 2871, 2853, 1737, 1507, and 1156 cm-1; HRMS (ESI) calcd for C23H41NO2Sn?Na+ 506.2051, found 506.2078.

References:

Izgu, Enver Cagri;Hoye, Thomas R. [Tetrahedron Letters,2012,vol. 53,# 37,p. 4938 - 4941] Location in patent:supporting information