Title: Rhodium‐Catalyzed Nondecarbonylative Addition Reaction of ClCOCOOC<sub>2</sub>H<sub>5</sub> to Alkynes
Abstract: Abstract Addition of ethoxalyl chloride (ClCOCOOEt) to terminal alkynes at 60 °C in the presence of a rhodium( I )–phosphine complex catalyst chosen from a wide range affords 4‐chloro‐2‐oxo‐3‐alkenoates regio‐ and stereoselectively. Functional groups such as chloro, cyano, alkoxy, siloxy, and hydroxy are tolerated. The oxidative addition of ethoxalyl chloride to [RhCl(CO)(PR 3 ) 2 ] proceeds readily at 60 °C or room temperature and gives [RhCl 2 (COCOOEt)(CO)(PR 3 ) 2 ] (PR 3 = PPh 2 Me, PPhMe 2 , PMe 3 ) complexes in high yields. The structure of [RhCl 2 (COCOOEt)(CO)(PPh 2 Me) 2 ] was confirmed by X‐ray crystallography. Thermolysis of these ethoxalyl complexes has revealed that those ligated by more electron‐donating phosphines are fairly stable against decarbonylation and reductive elimination. [RhCl 2 (COCOOEt)(CO)(PPh 2 Me) 2 ] reacts with 1‐octyne at 60 °C to form ethyl 4‐chloro‐2‐oxo‐3‐decenoate. The catalysis is therefore proposed to proceed by oxidative addition of ethoxalyl chloride, insertion of an alkyne into the ClRh bond of the resulting intermediate, and reductive elimination of alkenyl‐COCOOEt.
Publication Year: 2005
Publication Date: 2005-04-05
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 44
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