Liebeskind catalyst

Acetoacetic ester condensation. Durst and Liebeskind have used this phase-transfer catalyst in a solid-liquid phase acetoacetic ester condensation. In the... 

Rhodium catalysis is also of crucial importance in the conceptually new type of synthesis of cyclohepta-2,4-dien-l-ones (e. g. 12) by Huffman and Liebeskind. [8] The rearrangement of 4-cyclopropyl-2-cyclobuteno-nes such as 11, which are accessible in a few steps from squaric acid, [9] is similarly achieved with Wilkinson s catalyst (Scheme... 

By using the Liebeskind catalyst copper(I) thiophene-2-carboxylate (copper salt of L8), the coupling reaction of vinyl iodides and amides proceeded smoothly to give the corresponding enamides (Table 9.7, entry 1) [37]. CuI/DMEDA (Lll) was another efficient catalytic system for the coupling of vinyl halides with amides (entry 2) [38]. 

Liebeskind reported a copper-catalyzed Chan-Lam C-N crosscoupling methodology for JV-imination of boronic acids by using oxime O-carboxylates 291 as iminating agents and either Cu(I)-thiophene-2-carboxylate (CuTC) or Cu(OAc)2 as the catalyst under nonbasic and nonoxidizing conditions.Subsequently, the A-alkenylated a,3-unsaturated ketoxime 0-pentafluorobenzoates 293, were preeursors in a cascade reaction for the one-pot synthesis of tri-, tetra-, and penta-substituted pyridines 295 in moderate to excellent isolated yields. 

The first example of a Liebeskind-Srogl cross-coupling reaction in water was reported (13JHC1368). Specifically, 2-(methylthio)pyridine and 2-(methylthio)benzothiazole were treated with a series of arylboronic acids in the presence of Pd(0) catalyst and thiophene-2-carboxylate. 

In 2000, inspired by the work of Liebeskind [31], Wender and co-workers reported [32] an intramolecular Rh-catalyzed [6-1-2] cycloaddition reaction between vinylcyclobutanone and terminal aUcenes (Scheme 5). In this transformation 5 mol% [Rh(CO)2Cl]2, 10 mol% PPhs, and 10 mol% AgOTf were employed and cyclooctenone 24 was afforded in 92% yield as a single diastereoisomer. Besides sulfonamides, other linkers such as ether and geminal diesters were also found to be compatible with this reaction condition using specified catalyst precursors. 

Although palladium " and copper-catalyzed cross-coupling of amides and vinyl halides are possible, copper catalysis appears to be the most spread. On the basis of the precedents reported by Ogawa [150], Porco developed an efficient approach for the assembly of enamides using Liebeskind catalyst, copper(I) thiophene car-boxylate ([CuTC]), CS2CO3 and disubtituted ( )-vinyl iodides in NMP or DMSO. Using this protocol, a series of ( )-enamides could be prepared in moderate yields under mild conditions (Scheme 4.29) [144, 145]. Under these conditions, the coupling of 2-pyrrolidine and ( )-l-iodohept-l-ene takes place in 99 % yield. 

It is reported in literature that additives like LiCl or Cu(I) salts can have a dramatic influence on the coupling. The copper effect in Stille coupling reactions was investigated by Farina and Liebeskind and coworkers. For instance in the reaction of iodobenzene and vinyltributyltin in dioxane at 50 °C catalyzed by Pd2(dba)3 in presence of a strong ligand like PPhs, it was found that the addition of 2 molar equivalents of Cul per mol of catalyst led to a > 100 fold increase in reaction rate. 

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