Synthesis
To a solution of ethyl cyclobutanecarboxylate (10 g) in carbon tetrachloride (100 mL) was sequentially added N-bromosuccinimide (NBS, 20.83 g) and azobisisobutyronitrile (AIBN, 1.281 g). The reaction mixture was stirred at 80 °C for 2 hours. Upon completion of the reaction, the reaction was quenched by the addition of water (50 mL) and the mixture was extracted with ethyl acetate (3 x 50 mL). The organic phases were combined and washed sequentially with saturated sodium bicarbonate solution (50 mL), water (50 mL) and saturated saline (50 mL), dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate=100:1) to afford the target product ethyl 1-bromocyclobutanecarboxylate (10 g) as a yellow oil.1H NMR (400MHz, CDCl3) δ: 4.26 (q, J=14.4,7.2Hz, 2H), 2.95-2.88 (m, 2H), 2.67- 2.59 (m, 2H), 2.26-2.21 (m, 1H), 1.91-1.86 (m, 1H), 1.32 (t, J=7.2Hz, 3H).
References
[1] Journal of Organic Chemistry, 2012, vol. 77, # 23, p. 11002 - 11005
[2] Chemical Communications, 2015, vol. 51, # 42, p. 8773 - 8776
[3] Organic Letters, 2016, vol. 18, # 9, p. 2040 - 2043
[4] Patent: WO2018/15411, 2018, A1. Location in patent: Paragraph 0165; 0166; 0167; 0168; 0169; 0170
[5] ACS Medicinal Chemistry Letters, 2016, vol. 7, # 11, p. 988 - 993
