Brønsted Acid‐Catalyzed Carbocyclization of 2‐Alkynyl Biaryls
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Abstract Ortho‐alkynyl biaryls react in the presence of catalytic amount of Brønsted acids to give phenanthrenes in high yields under mild conditions. The activity and selectivity of this transformation are governed by the substitution pattern of the diarylalkyne moiety. Selectivity shifts are observed between the carbophilic Lewis and Brønsted acid‐catalyzed cycloisomerization involving alkyne activation. magnified imageKeywords:
Cycloisomerization
Phenanthrenes
Moiety
Brønsted–Lowry acid–base theory
Alkyne
Abstract For Abstract see ChemInform Abstract in Full Text.
Phenanthrenes
Cycloisomerization
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Abstract A novel gold‐catalyzed 6‐ exo ‐ dig cycloisomerization of o ‐propargylbiaryls has been developed that provides ready access to functionalized phenanthrenes in largely good to excellent yields. Notable features of this method are readily available starting materials, mild reaction conditions, and broad substrate scope.
Cycloisomerization
Phenanthrenes
Scope (computer science)
Dig
Reaction conditions
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Readily available o'-alkenyl-o-alkynylbiaryls, a particular type of 1,7-enynes, undergo a selective cycloisomerization reaction in the presence of a gold(I) catalyst to give interesting phenanthrene and dihydrophenanthrene derivatives in high yields. The solvent used provokes a switch in the evolution of the gold intermediate and plays a key role in the reaction outcome.
Cycloisomerization
Phenanthrenes
Biphenyl
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Abstract Various functionalized phenanthrenes are synthesized with good functional group tolerance by a general and practical method starting from readily available o‐propargyl biaryls under mild reaction conditions.
Phenanthrenes
Cycloisomerization
Propargyl
Functional group
Reaction conditions
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Brønsted–Lowry acid–base theory
Lone pair
Electron pair
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Abstract Ruthenium‐catalyzed cycloisomerization of 2‐ethynylbiaryls was investigated to identify an optimal ruthenium catalyst system. A combination of [η 6 ‐( p ‐cymene)RuCl 2 (PR 3 )] and two equivalents of AgPF 6 effectively converted 2‐ethynylbiphenyls into phenanthrenes in chlorobenzene at 120 °C over 20 h. Moreover, 2‐ethynylheterobiaryls were found to be favorable substrates for this ruthenium catalysis, thus achieving the cycloisomerization of previously unused heterocyclic substrates. Moreover, several control experiments and DFT calculations of model complexes were performed to propose a plausible reaction mechanism.
Cycloisomerization
Phenanthrenes
Chlorobenzene
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Abstract Ortho‐alkynyl biaryls react in the presence of catalytic amount of Brønsted acids to give phenanthrenes in high yields under mild conditions. The activity and selectivity of this transformation are governed by the substitution pattern of the diarylalkyne moiety. Selectivity shifts are observed between the carbophilic Lewis and Brønsted acid‐catalyzed cycloisomerization involving alkyne activation. magnified image
Cycloisomerization
Phenanthrenes
Moiety
Brønsted–Lowry acid–base theory
Alkyne
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A rhodium and Brønsted acid catalyzed one-pot cycloisomerization/hetero-Diels–Alder reaction of 1,6-enynes with unactivated aldehydes was established under mild conditions. This one-pot catalytic protocol produced a wide variety of annulated dihydropyrans from readily available starting materials in a highly atom economical manner.
Cycloisomerization
Brønsted–Lowry acid–base theory
Diels–Alder reaction
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Brønsted–Lowry acid–base theory
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Abstract Numerous functionalized phenanthrenes are obtained via In(III)‐catalyzed electrophile‐promoted nucleophilic cyclization of o‐propargylbiaryls.Various functionalized groups are tolerated on the alkynyl carbon.
Phenanthrenes
Cycloisomerization
Dig
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