Yield:-

Steps:

Multi-step reaction with 2 steps
1: 96 percent / DMAP, pyridine / 48 h / Ambient temperature
2: 93 percent / (COCl)2, Et₃N, DMSO / CH₂Cl₂ / -70 °C

References:

Gueller, Rolf;Binggeli, Alfred;Breu, Volker;Bur, Daniel;Fischli, Walter;Hirth, Georges;Jenny, Christian;Kansy, Manfred;Montavon, Francois;Mueller, Marcel;Oefner, Christian;Stadler, Heinz;Vieira, Eric;Wilhelm, Maurice;Wostl, Wolfgang;Maerki, Hans Peter [Bioorganic and Medicinal Chemistry Letters,1999,vol. 9,# 10,p. 1403 - 1408]