Reaction #1089

Reaction equation

hydrochloric acid

triisopropyl borate

6-methoxybenzo[b]thiophene

n-butyllithium

→

6-methoxybenzo[b]thiophene-2-boronic acid

Yield 71.0%

Solvents

ethyl acetate

tetrahydrofuran

Conditions

Workup

1. 1
   OtherThe layers were separated
2. 2
   Dryingthe organic layer was dried over sodium sulfate
3. 3
   ConcentrationConcentration in vacuo
4. 4
   Otherproduced a white solid
5. 5
   Otherthat was triturated from ethyl ether hexanes
6. 6
   FiltrationFiltration

Procedure

To a solution of 6-methoxybenzo[b]thiophene (18.13 g, 0.111 mol) in 150 mL of anhydrous tetrahydrofuran (THF) at -60° C. was added n-butyllithium (76.2 mL, 0.122 mol, 1.6M solution in hexanes), dropwise via syringe. After stirring for 30 minutes, triisopropyl borate (28.2 mL, 0.122 mol) was introduced via syringe. The resulting mixture was allowed to gradually warm to 0° C. and then distributed between 1N hydrochloric acid and ethyl acetate (300 mL each). The layers were separated, and the organic layer was dried over sodium sulfate. Concentration in vacuo produced a white solid that was triturated from ethyl ether hexanes. Filtration provided 16.4 g (71%) of 6-methoxybenzo[b]thiophene-2-boronic acid as a white solid. mp 200° C. (dec). 1H NMR (DMSO-d6) d 7.83 (s, 1H), 7.78 (d, J=8.6 Hz, 1H), 7.51 (d, J=2.0 Hz, 1H), 6.97 (dd, J=8.6, 2.0 Hz, 1H), 3.82 (s, 3H). FD mass spec: 208.

Source