Yield: 65%

Reaction Conditions:

with hydrogen bromide at 80; for 3 h;

Steps:

A.1 Step 1 Synthesis of Compound A-2
Compound 1 (5.0 g, 73.4 mmol) was addedIn a solution of 47% hydrobromic acid (20 ml),The reaction solution was reacted at 80 ° C for 3 h.Distilled under normal pressure,Collect 60-70 ° C fractions,A colorless liquid of 6.2 g was obtained in a yield of 65%.

References:

Shenzhen Tajirui Bio-pharmaceutical Co., Ltd.;Wang Yihan;Liu Zhiqiang CN110256408, 2019, A Location in patent:Paragraph 0189; 0190; 0191