Naphthalene → 2-Ethoxynaphthalene

HRID 1467423Notes

Reaction equation

HRID 1467423 reaction equation
[CH:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH:4]=[CH:3][CH:2]=1.CC1C=CC2C(=CC=CC=2)C=1.[CH:22]1[C:31]2[C:26](=[CH:27][CH:28]=[CH:29][CH:30]=2)[CH:25]=[CH:24][C:23]=1[OH:32]>>[CH2:23]([O:32][C:7]1[CH:8]=[CH:9][C:10]2[C:5](=[CH:4][CH:3]=[CH:2][CH:1]=2)[CH:6]=1)[CH3:22].[CH:22]1[C:31]2[C:26](=[CH:27][CH:28]=[CH:29][CH:30]=2)[CH:25]=[CH:24][C:23]=1[OH:32]

Participants

5

Reactant 3

HCID 931NaphthaleneHCID 70552-MethylnaphthaleneHCID 86632-Naphthol

Product 2

HCID 71292-EthoxynaphthaleneHCID 86632-Naphthol

Procedure

Silylations of aryl alkyl ethers at elevated temperatures were conducted under the conditions applied to diaryl ethers to probe the cleavage selectivity of sp2 versus sp3 C—O bond. At the elevated temperatures of these experiments, the reaction of 2-methoxynaphthalene gave 2-naphthol as the major product in moderate yield (Scheme 1). GC-MS analysis of the crude reaction mixture indicated the presence of trace amounts of naphthalene along with 2-methylnaphthalene and further reduced species, including products of partial aromatic reduction. Compounds presumably derived from 2-naphthol silylation were also detected. Likewise, cleavage of 2-ethoxynapthalene under the same conditions gave 2-naphthol in slightly higher yield, but with the same or analogous side products. Sterically bulkier ethers were investigated to probe the versatility and possible mechanism of the C—O bond cleavage. Despite the large alkyl substituent adjacent to the ether oxygen, reaction of 2-neopentyloxynaphthalene provided 2-naphthol in approximately the same yield as with the less bulky substrates. Even 2-tert-butyloxynapthalene was cleaved to give the expected naphthol in 55% yield (Scheme 1). Control experiments performed at identical conditions but without triethylsilane provided 2-naphthol in cases of 2-ethoxy- and 2-tert-butyloxynapthalene albeit with substantially diminished yields. Since 2-methoxy- and 2-neopentyloxy-substrates remained intact in such silane-free cleavages, a b elimination mechanism is likely to be operative. When attempting to reduce 4-tert-butyl and 4-methyl anisoles under the standard conditions, the yields of the corresponding phenols were high, likely because of more challenging silylation of the substituted phenyl ring for the steric reasons (Scheme 2).

Workup

  1. customin moderate yield (Scheme 1)
  2. customGC-MS analysis of the crude reaction mixture

Sources & evidence

ORD record
ord-5e9ccce244d74e53b856376eb4cb5933
Source dataset
uspto-grants-2015_04
Patent number
US09000167B2

Reaction notes

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