Boron tribromide → 3-Benzothiazol-2-yl-5,6-dihydro-8H-[1,2,4]triazolo[4,3-a]pyrazine

HRID 394539Notes

Reaction equation

HRID 394539 reaction equation
C(OC([N:11]1[CH2:16][CH2:15][N:14]2[C:17]([C:20]3[S:21][C:22]4[CH:28]=[CH:27][CH:26]=[CH:25][C:23]=4[N:24]=3)=[N:18][N:19]=[C:13]2[CH2:12]1)=O)C1C=CC=CC=1.S1C2C=CC=CC=2N=C1C(NN)=O.B(Br)(Br)Br>ClCCl>[S:21]1[C:22]2[CH:28]=[CH:27][CH:26]=[CH:25][C:23]=2[N:24]=[C:20]1[C:17]1[N:14]2[CH2:15][CH2:16][NH:11][CH2:12][C:13]2=[N:19][N:18]=1

Participants

5

Reactant 3

HCID 25134Boron tribromideHCID 3514191,3-Benzothiazole-2-carbohydrazideHCID 572446703-Benzothiazol-2-yl-5,6-dihydro-8H-[1,2,4]triazolo[4,3-a]pyrazine-7-carboxylic acid benzyl ester

Product 1

HCID 223287923-Benzothiazol-2-yl-5,6-dihydro-8H-[1,2,4]triazolo[4,3-a]pyrazine

Reagents, catalysts & solvents 1

HCID 6344DichloromethaneSolvent

Procedure

To a solution of 3-benzothiazol-2-yl-5,6-dihydro-8H-[1,2,4]triazolo[4,3-a]pyrazine-7-carboxylic acid benzyl ester (prepared according to the method of Example 259, Step B, 580 mg, contaminated with benzothiazole-2-carboxylic acid hydrazide) in dichloromethane (10 mL) at 0° C. was added a solution of boron tribromide (1 M in dichloromethane, 4.45 mL, 4.45 mmol). This mixture was warmed to room temperature overnight, quenched by addition of water, and concentrated. The residual aqueous layer was washed with ether (6×), neutralized with saturated aqueous sodium bicarbonate, and extracted with 10% isopropanol/chloroform (3×). The combined organic extracts were dried over sodium sulfate, filtered, evaporated, and purified by flash column chromatography (1→10% methanol/chloroform) to give 175 mg (36%, two steps) of the title compound of Example 259, Step C as a white solid. 1H NMR (CDCl3, 300 MHz) δ 8.05 (d, 1H), 7.96 (d, 1H), 7.57-7.41 (c, 2H), 4.62 (t, 2H), 4.36 (s, 2H), 3.35 (t, 2H); MS (APCI) 258 (MH+).

Workup

  1. customat 0° C.
  2. customquenched by addition of water
  3. concentrationconcentrated
  4. washThe residual aqueous layer was washed with ether (6×)
  5. extractionextracted with 10% isopropanol/chloroform (3×)
  6. dry with materialThe combined organic extracts were dried over sodium sulfate
  7. filtrationfiltered
  8. customevaporated
  9. custompurified by flash column chromatography (1→10% methanol/chloroform)

Sources & evidence

ORD record
ord-be3e0d2f62734133a421976a31967d0f
Source dataset
uspto-grants-2003_08
Patent number
US06602875B2

Reaction notes

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