Ethyl 3-(bromophenyl)acetate → (3-Bromophenyl)acetaldehyde

HRID 2085822Notes

Reaction equation

HRID 2085822 reaction equation
[Br:1][C:2]1[CH:3]=[C:4]([CH2:8][C:9](OCC)=[O:10])[CH:5]=[CH:6][CH:7]=1.[H-].C([Al+]CC(C)C)C(C)C>>[Br:1][C:2]1[CH:3]=[C:4]([CH2:8][CH:9]=[O:10])[CH:5]=[CH:6][CH:7]=1

Participants

3

Reactant 2

HCID 11470552Ethyl 3-(bromophenyl)acetate2×HCID 21225700Diisobutylaluminumhydride

Product 1

HCID 20387554(3-Bromophenyl)acetaldehyde

Procedure

Important starting materials for the synthesis of the preferred compounds of the invention are 6-bromo-1,2,3,4-tetrahydro-1,1-dimethylnaphthalene (Compound F), 7-bromo-3,4-dihydro-4,4-dimethylnaphthalen-1-one (Compound G), and the isomeric bromo compound, 6-bromo-3,4-dihydro-4,4-dimethylnaphthalen-1(2H)-one (Compound H). Compound G can be obtained as described in J. Med Chem. 1995, 38, 4764-4767, and as shown in Reaction Scheme 1. Thus, referring now specifically to Reaction Scheme 1, ethyl 3-bromophenylacetate (Compound B, made by esterification of 3-bromophenylacetic acid) is reduced with diisobutylaluminum hydride (DEBAL H) to yield (3-bromophenyl)acetaldehyde. (3-Bromophenyl)acetaldehyde is reacted in a Wittig reaction with (carbethoxymethylene)triphenylphosphorane to provide a mixture of E and Z ethyl 4-(3-bromophenyl)but-2-enoates. The latter compounds are hydrogenated to yield ethyl 4-(3-bromophenyl)butanoate (Compound D). Compound D is reacted with the Grignard reagent derived from methylbromide to give the tertiary alcohol 5-(3-bromophenyl)-2-methylpentan-2-ol (Compound E) (It should be apparent to those skilled in the art, that the choice of the Grignard reagent used in this reaction step determines the nature of the R1 substituent in the resulting compounds of the invention.) Compound E is then treated with acid to cyclize it and to form 6-bromo-1,2,3,4-tetrahydro-1,1-dimethylnaphthalene (Compound F). Compound F is oxidized with chromium trioxide to yield 7-bromo-3,4-dihydro-4,4-dimethylnaphthalen-1(2H)-one (Compound G). The isomeric compound, 6-bromo-3,4-dihydro-4,4-dimethylnaphthalen-1(2H)-one (Compound H) can be, obtained, starting with ethyl (4-bromophenyl)acetate, in accordance with the sequence of reactions illustrated in Reaction Scheme 1 for Compound G. 6-Bromo-3,4-dihydro-4,4-dimethylnaphthalen-1(2H)-one (Compound H) can also be obtained in accordance with the published literature procedure: Mathur et al. Tetrahedron, 41, 1509-1516 (1985).

Workup

  1. custom1995, 38, 4764-4767, and as shown in Reaction Scheme 1

Sources & evidence

ORD record
ord-1adcb112730e4270b2889be62b807afd
Source dataset
uspto-grants-2004_04
Patent number
US06720425B2

Reaction notes

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