- Triflic acid mediated sequential cyclization of ortho-alkynylarylesters with ammonium acetate
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A triflic acid (TfOH) mediated sequential cyclization of ortho-alkynylarylesters and ammonium acetate (NH4OAc) was reported. The reaction took place via a Br?nsted acid-mediated intramolecular cyclization of ortho-alkynylarylesters followed by an ammonium acetate participated substitution reaction, forming isoquinolin-1-ones as the major products. Different from most of the known synthetic methods of isoquinolin-1-ones, no metal catalyst was required in the reported reaction. The regioisomers – isoindolin-1-ones were obtained together with isoquinolin-1-ones in a few cases. The intermediate compounds – isochromen-1-ones and isobenzofuran-1-ones were also isolated. The interconversion experiments showed that the regioisomers formed during the Br?nsted acid induced intramolecular cyclization of ortho-alkynylarylesters. A natural product – ruprechstyril was prepared in a moderate yield employing the new method.
- Domaradzki, Maciej E.,Liu, Xiaochen,Ong, Jiye,Yu, Gyeongah,Zhang, Gan,Simantov, Ariel,Perl, Eliyahu,Chen, Yu
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- Halocyclization of methyl 2-alkynylbenzoates to isocoumarins using cupric halides
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Treatment of methyl 2-alkynylbenzoates with two to three equivalents of CuX2 (X = Cl or Br) in refluxing acetonitrile gave isocoumarins 2 in good to excellent chemical yields.
- Chin, Ling-Yu,Lee, Chia-Ying,Lo, Yu-Hsiang,Wu, Ming-Jung
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p. 643 - 648
(2009/05/11)
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- Rhodium Carbenoid Mediated Cyclizations of o-Alkynyl-Substituted α-Diazoacetophenones
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o-Alkynyl-substituted α-diazoacetophenones undergo facile cyclization to indenone derivatives upon treatment with catalytic quantities of Rh(II) carboxylates.A variety of structural influences were encountered by varying the nature of the substituent group attached to the alkyne carbon atom.The cyclization reaction involves addition of a rhodium stabilized carbenoid onto the acetylenic ?-bond to generate a vinyl carbenoid.The vinyl carbenoid was found to undergo both CH and CC migration as well as δ-CH insertion into the alkyl backbone.Different catalysts were shown to result in significant variation in the product ratios for these reactions.Treatment of o-(5-(allyloxy)-1-pentynyl)-α-diazoacetophenone with rhodium(II) mandelate afforded 2-(2-propen-1-yl)-2-(1-oxo-1H-indenyl)-2,3,4,5-tetrahydrofuran in high yield.The formation of this compound involves initial formation of a vinyl carbenoid which reacts with the neighboring oxygen atom to give an oxonium ylide which subsequently undergoes a 2,3-sigmatropic rearrangement.When 2-ethynyl-α-diazoacetophenone is used, only products derived from 6-endo closure are observed.Substituted o-alkynyl α-diazoacetophenones give products derived from 5-exo cyclization.The mode of ring closure is controlled by both steric and electronic factors.
- Padwa, Albert,Krumpe, Keith E.,Kassir, Jamal M.
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p. 4940 - 4948
(2007/10/02)
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