p-Toluenesulfonic acid → 6-Bromo-2H-1-benzopyran-3(4H)-one

HRID 444896Notes

Reaction equation

HRID 444896 reaction equation
[Br:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[O:8][CH2:7][CH2:6][C:5]2=O.[BH4-].[Na+].CC1C=CC(S(O)(=O)=[O:23])=CC=1.BrC1C=C2C(=CC=1)OCC=C2.C[N+]1([O-])CCOCC1>O=[Os](=O)(=O)=O.O.CC(C)=O.CC(O)(C)C>[Br:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][CH:11]=1)[O:8][CH2:7][C:6](=[O:23])[CH2:5]2

Participants

8

Reactant 5

HCID 6101p-Toluenesulfonic acid2×HCID 82029Methyl morpholine oxideHCID 41974516-bromo-3,4-dihydro-2H-1-benzopyran-4-one2×HCID 4311764Sodium borohydrideHCID 102422416-bromo-2H-chromene

Product 1

HCID 584666226-Bromo-2H-1-benzopyran-3(4H)-one

Reagents, catalysts & solvents 2

HCID 30318Osmium TetroxideCatalystHCID 86602953Acetone tBuOH WaterSolvent

Procedure

The starting material 6-bromochroman-3-one (5A) was prepared from 6-bromochroman-4-one in a manner similar to that described in the literature (Synthesis, 1980, 621): 6-bromochroman-4-one was reduced with NaBH4 (1.2 eq, MeOH-DCM, 0° C. to RT, 2 h) and then eliminated with pTsOH (cat., toluene, reflux, 3 h, 90% for 2-steps). The resulting 6-bromochromene was subjected to osmylation (cat. OsO4, 1 eq. NMO, water-acetone-tBuOH, RT, overnight) and subsequent treatment with pTsOH (cat., toluene, reflux, 15 min, 86% for 2-steps) to provide 6-bromochroman-3-one (5A).

Workup

  1. customthat described in the literature (Synthesis, 1980, 621)

Sources & evidence

ORD record
ord-3dad9be9879c49c19eb5457bd90dc1e0
Source dataset
uspto-grants-2013_07
Patent number
US08476274B2

Reaction notes

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