Sodium cyanoborohydride → 1,2-Dibromo-4,4-dimethylcyclopentene

HRID 1901103Notes

Reaction equation

HRID 1901103 reaction equation
[Br:1][C:2]1[CH2:6][C:5]([CH2:9]I)([CH2:7]I)[CH2:4][C:3]=1[Br:11].C([BH3-])#N.[Na+]>CN(C)P(N(C)C)(N(C)C)=O.O>[Br:1][C:2]1[CH2:6][C:5]([CH3:9])([CH3:7])[CH2:4][C:3]=1[Br:11]

Participants

5

Reactant 2

HCID 5003444Sodium cyanoborohydrideHCID 138660801,2-Dibromo-4,4-di(iodomethyl)cyclopentene

Product 1

HCID 138660731,2-Dibromo-4,4-dimethylcyclopenteneYield 70.1%

Reagents, catalysts & solvents 2

HCID 962WaterSolventHCID 12679HexamethylphosphoramideSolvent

Procedure

Under nitrogen, a stirred solution of 3.7 g (7.3 mmol) of 1,2-dibromo-4,4-di(iodomethyl)cyclopentene (Step 7) and 1.3 g (20.6 mmol) of sodium cyanoborohydride in 15 mL of hexamethylphosphoramide (HMPA) was heated to 100° C. in an oil bath overnight. The reaction was cooled, diluted with 50 mL of water, and extracted 5 times with ethyl acetate/hexane (1:5). The combined extracts were washed 3 times with water, dried (Na2SO4), and concentrated in vacuo. Purification by silica gel chromatography (Waters Prep-500) with hexane gave 1.3 g (70%) of 1,2-dibromo-4,4-dimethylcyclopentene (16 in Synthetic Scheme V) as a colorless oil: NMR (CDCl3) δ1.16 (s, 6H), 2.44 (s, 4H); MS (EI) m/e (rel intensity) 256 (24), 254 (63), 252 (44), 175 (26), 173 (29), 94 (100).

Workup

  1. temperatureThe reaction was cooled
  2. extractionextracted 5 times with ethyl acetate/hexane (1:5)
  3. washThe combined extracts were washed 3 times with water
  4. dry with materialdried (Na2SO4)
  5. concentrationconcentrated in vacuo
  6. customPurification by silica gel chromatography (Waters Prep-500) with hexane

Sources & evidence

ORD record
ord-94396c11a0e74f5297d33f8f397a9f19
Source dataset
uspto-grants-1996_11
Patent number
US05576339

Reaction notes

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