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1,5-Dibromopentane → (R)-(+)-6-[(5-bromopentyl)oxy]-3,4-dihydro-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid methyl ester

HRID 2231918
Notes
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Reaction equation

HRID 2231918 reaction equation
[CH3:1][O:2][C:3]([C@@:5]1([CH3:19])[CH2:10][CH2:9][C:8]2[C:11]([CH3:18])=[C:12]([OH:17])[C:13]([CH3:16])=[C:14]([CH3:15])[C:7]=2[O:6]1)=[O:4].C(=O)([O-])[O-].[K+].[K+].C1OCCOCCOCCOCCOCCOC1.[Br:44][CH2:45][CH2:46][CH2:47][CH2:48][CH2:49]Br>O.CCOCC.C(#N)C>[CH3:1][O:2][C:3]([C@@:5]1([CH3:19])[CH2:10][CH2:9][C:8]2[C:11]([CH3:18])=[C:12]([O:17][CH2:49][CH2:48][CH2:47][CH2:46][CH2:45][Br:44])[C:13]([CH3:16])=[C:14]([CH3:15])[C:7]=2[O:6]1)=[O:4]
ParticipantsProcedureWorkupSources & evidenceReaction notes

Participants

8

Reactant 4

HCID 81001,5-DibromopentaneHCID 11430Potassium CarbonateHCID 2855718-Crown-6HCID 14308591(R)-(+)-methyl 3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylate

Product 1

HCID 14329716(R)-(+)-6-[(5-bromopentyl)oxy]-3,4-dihydro-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid methyl esterYield 95.6%

Reagents, catalysts & solvents 3

HCID 962WaterSolventHCID 3283Diethyl EtherSolventHCID 6342AcetonitrileSolvent

Procedure

A mixture of 6.5 g (24.6 mmoles) of (R)-(+)-6-hydroxy-3,4-dihydro-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid methyl ester, 10.37 g (75.1 mmoles) of anhydrous potassium carbonate, 1.12 g of 18-crown-6, 39.3 ml (0.2 mole) of 1,5-dibromopentane, and 150 ml of acetonitrile was stirred and refluxed for 21 hours. After being cooled, the mixture was treated with ether and water. The organic layer was separated, washed with water and brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The residue (68 g) was purified first by column chromatography on silica gel (400 g; eluting with 49:1 toluene-ethyl acetate) and then by preparative HPLC on silica gel using 9:1 hexane-ethyl acetate as the mobile phase. There was obtained 9.71 g (95.6%) of (R)-(+)-6-[(5-bromopentyl)oxy]-3,4-dihydro-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid methyl ester as a solid. Recrystallization from ethanol gave a colorless solid mp 64°- 65.5° C., [α]D25 +36.37° (c2, CHCl3).

Workup

  1. temperaturerefluxed for 21 hours
  2. temperatureAfter being cooled
  3. customThe organic layer was separated
  4. washwashed with water and brine
  5. dry with materialdried over anhydrous magnesium sulfate
  6. filtrationfiltered
  7. concentrationconcentrated under reduced pressure
  8. customThe residue (68 g) was purified first by column chromatography on silica gel (400 g; eluting with 49:1 toluene-ethyl acetate)

Sources & evidence

ORD record
ord-25b2774fe3a24a4e8ce7b3b11793e945
Source dataset
uspto-grants-1988_11
DOI
10.6084/m9.figshare.5104873.v1
Patent number
US04785017

Reaction notes

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On this pageParticipantsProcedureWorkupSources & evidenceReaction notes