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Selective oxidative homo- and cross-coupling of phenols with aerobic catalysts.

Lee YE, Cao T, Torruellas C, Kozlowski MC - J. Am. Chem. Soc. (2014)

Bottom Line: Simple catalysts that use atom-economical oxygen as the terminal oxidant to accomplish selective ortho-ortho, ortho-para, or para-para homo-couplings of phenols are described.In addition, chromium salen catalysts have been discovered as uniquely effective in the cross-coupling of different phenols with high chemo- and regioselectivity.

View Article: PubMed Central - PubMed

Affiliation: Penn Merck High Throughput Experimentation Laboratory, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.

ABSTRACT
Simple catalysts that use atom-economical oxygen as the terminal oxidant to accomplish selective ortho-ortho, ortho-para, or para-para homo-couplings of phenols are described. In addition, chromium salen catalysts have been discovered as uniquely effective in the cross-coupling of different phenols with high chemo- and regioselectivity.

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Amounts of ortho–ortho (o–o) and PK products fromTable 1, entry 7 with 36 catalysts using O2. Beige shading indicates PK is the major product.
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fig2: Amounts of ortho–ortho (o–o) and PK products fromTable 1, entry 7 with 36 catalysts using O2. Beige shading indicates PK is the major product.

Mentions: With entries 7 and 9from Table 1, an additionalmajor peak was seen in the HPLC spectra from the initial screening.Re-examination of the data rapidly identified catalysts selectivefor this compound (beige highlights in Figure 2). This material was ultimately determined to be the tricyclic Pummererketone1,2a (PK), which forms via ortho–para coupling followed by a 1,4-addition(Scheme 2). Optimizedconditions provided this PK with high efficiency (Table 1, entries 8, 10, 12). Notably, this motif is found in severalnatural products such as the galanthamines and usnic acids.11 On the other hand, when the para-position is unsubstituted, ortho–para bisphenols are generated (entry 5). Notably,different catalysts permit control of ortho–ortho vs ortho–para coupling(Table 1, entries 4/5, 7/8, 9/10).


Selective oxidative homo- and cross-coupling of phenols with aerobic catalysts.

Lee YE, Cao T, Torruellas C, Kozlowski MC - J. Am. Chem. Soc. (2014)

Amounts of ortho–ortho (o–o) and PK products fromTable 1, entry 7 with 36 catalysts using O2. Beige shading indicates PK is the major product.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4227839&req=5

fig2: Amounts of ortho–ortho (o–o) and PK products fromTable 1, entry 7 with 36 catalysts using O2. Beige shading indicates PK is the major product.
Mentions: With entries 7 and 9from Table 1, an additionalmajor peak was seen in the HPLC spectra from the initial screening.Re-examination of the data rapidly identified catalysts selectivefor this compound (beige highlights in Figure 2). This material was ultimately determined to be the tricyclic Pummererketone1,2a (PK), which forms via ortho–para coupling followed by a 1,4-addition(Scheme 2). Optimizedconditions provided this PK with high efficiency (Table 1, entries 8, 10, 12). Notably, this motif is found in severalnatural products such as the galanthamines and usnic acids.11 On the other hand, when the para-position is unsubstituted, ortho–para bisphenols are generated (entry 5). Notably,different catalysts permit control of ortho–ortho vs ortho–para coupling(Table 1, entries 4/5, 7/8, 9/10).

Bottom Line: Simple catalysts that use atom-economical oxygen as the terminal oxidant to accomplish selective ortho-ortho, ortho-para, or para-para homo-couplings of phenols are described.In addition, chromium salen catalysts have been discovered as uniquely effective in the cross-coupling of different phenols with high chemo- and regioselectivity.

View Article: PubMed Central - PubMed

Affiliation: Penn Merck High Throughput Experimentation Laboratory, Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.

ABSTRACT
Simple catalysts that use atom-economical oxygen as the terminal oxidant to accomplish selective ortho-ortho, ortho-para, or para-para homo-couplings of phenols are described. In addition, chromium salen catalysts have been discovered as uniquely effective in the cross-coupling of different phenols with high chemo- and regioselectivity.

Show MeSH