Hydrochloric Acid → (S)-(+)-3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid methyl ester

HRID 26383Notes

Reaction equation

HRID 26383 reaction equation
[CH3:1][C@@:2]([O:20]S(C)(=O)=O)([CH2:7][CH2:8][C:9]1[C:14](=O)[C:13]([CH3:16])=[C:12]([CH3:17])[C:11](=[O:18])[C:10]=1[CH3:19])[C:3]([O:5][CH3:6])=[O:4].[BH4-].[Na+].C[O-].[Na+].Cl>CO.[Cl-].[Na+].O.CCOCC>[CH3:6][O:5][C:3]([C@:2]1([CH3:1])[CH2:7][CH2:8][C:9]2[C:10]([CH3:19])=[C:11]([OH:18])[C:12]([CH3:17])=[C:13]([CH3:16])[C:14]=2[O:20]1)=[O:4]

Participants

8

Reactant 4

HCID 313Hydrochloric AcidHCID 4311764Sodium borohydrideHCID 10942334Sodium MethoxideHCID 56612147HCID 56612147, compound

Product 1

HCID 14308592(S)-(+)-3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid methyl esterYield 84.1%

Reagents, catalysts & solvents 3

HCID 887MethanolSolvent2×HCID 3283Diethyl EtherSolventHCID 57417360Sodium chloride; waterSolvent

Procedure

To a solution of 0.5g (1.4 mmoles) of (R)-(-)-methyl 2-methyl-2-[(methylsulfonyl)oxy]-4-(2,4,5-trimethyl-3,6-dioxo-1,4-cyclohexadien-1-yl)butanoate in 30 ml of methanol, at room temperature, was added a solution of 20.2 mg (0.53 mmole) of sodium borohydride in 10 ml of methanol, dropwise, with stirring. After stirring at room temperature for 50 min, 5.77 ml (7.73 mmoles) of 1.34 M methanolic sodium methoxide was added and stirring was continued for 2 hr, at room temperature. The resulting solution was acidifed with 1 N aqueous hydrochloric acid then poured into saturated brine and worked-up with ether in the usual manner. The crude, crystalline product (0.34g) was chromatographed on 20g of silica gel. Elution with 19:1 parts by volume toluene-ethyl acetate gave 0.311g (84.1%) of (S)-(+)-3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-carboxylic acid methyl ester as a colorless solid, mp 131-134°; [α]D25 -60.46° (c 3.88, CH3OH).

Workup

  1. stirringAfter stirring at room temperature for 50 min
  2. stirringstirring
  3. customThe crude, crystalline product (0.34g) was chromatographed on 20g of silica gel
  4. washElution with 19:1 parts by volume toluene-ethyl acetate

Sources & evidence

ORD record
ord-fbf5386acd1a4e59b9f9e590f7fdc273
Source dataset
uspto-grants-1979_04
Patent number
US04150050

Reaction notes

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