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Palladium-catalyzed synthesis of 2E-[(methoxycarbonyl)methylene]tetrahydrofurans: oxidative cyclization–methoxycarbonylation of 4-yn-1-ols versus cycloisomerization–hydromethoxylation

Authors
Journal
Journal of Organometallic Chemistry
0022-328X
Publisher
Elsevier
Publication Date
Identifiers
DOI: 10.1016/s0022-328x(99)00492-1
Keywords
  • Carbonylation
  • 2E-[(Methoxycarbonyl)Methylene]Tetrahydrofurans
  • 2-Methoxy-2-Methyltetrahydrofurans
  • Palladium
  • 4-Yn-1-Ols

Abstract

Abstract 4-Yn-1-ols bearing a terminal triple bond undergo oxidative cyclization–alkoxycarbonylation in methanol at 70°C and 100 atm of a 9:1 mixture of carbon monoxide and air in the presence of catalytic amounts of [PdI 4] 2− in conjunction with an excess of KI to give 2 E-[(methoxycarbonyl)methylene]tetrahydrofurans in good yields. A competing reaction, cycloisomerization–hydromethoxylation leading to 2-methoxy-2-methyltetrahydrofurans, can be easily curtailed by increasing the KI excess. The latter products can be prepared from 4-yn-1-ols and methanol in high yields using the same catalytic system and without KI excess in the absence of carbon monoxide.

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