Rhodium‐Catalyzed Nondecarbonylative Addition Reaction of ClCOCOOC₂H₅ to Alkynes

Abstract

Addition of ethoxalyl chloride (ClCOCOOEt) to terminal alkynes at 60 degrees 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 degrees 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 degrees 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 Cl--Rh bond of the resulting intermediate, and reductive elimination of alkenyl-COCOOEt.

Transition metals in organic synthesis: Highlights for the year 2005

“…Rhodium catalyzed the addition of ethoxallylchloride (Eq. (129)) [804] and of perfluorinated acid chlorides [805] to alkynes. Nickel catalyzed an alkylative carboxylation of alkynes using organozinc reagents and carbon dioxide (Eq.…”

Hydrolysis of Letrozole catalyzed by macrocyclic Rhodium (I) Schiff-base complexes

“…Rhodium complexes are versatile catalysts and can be used for several organic reactions, like oxidation [40], reduction [41], carbonylation [42], addition [43], hydroformylation [44], hydroboration [45] etc. The Wilkinson catalyst, RhCl(PPh 3 ) 3 is the classic example of a homogeneous hydrogenation catalyst [46].…”

Stereoselective Synthesis of β‐Chlorovinyl Ketones and Arenes by the Catalytic Addition of Acid Chlorides to Alkynes

“…Tanaka and co-workers showed that such reactions proceed with the retention of CO in the presence of the same catalyst when chloroformate esters, which are particularly electron-poor substrates, are used. [8] Over the following years, the Tanaka research group developed tailored procedures for the stereoselective, CO-retentive addition of ethoxalyl chloride, [9] perfluorinated acid chlorides, [10] and chloroacetyl chlorides [11] (Scheme 2, bottom).…”