Yield:-

Reaction Conditions:

with sulfuric acid at 0 - 20; for 1.5 h;

Steps:

18.2

The neat product of Step 1 was stirred and cooled to 0° C. in an ice bath. Once at the prescribed temperature, concentrated sulfuric acid (26 mL) was added dropwise. Upon completion of addition, the reaction mixture was stirred for 30 min. After this time, the ice bath was removed and the reaction mixture was allowed to warm to room temperature where it stirred for one hour. At the conclusion of this period, the reaction mixture was worked-up and the product isolated in the manner of Step 3, Preparation 15 (4.93 g, 68% yield for two steps). MS (E+) m/z: 160 (MH⁺); LC retention time (Method A): 1.64 min.

References:

US2005/187242,2005,A1 Location in patent:Page/Page column 39