Propargyl halides, cross-coupling reactions

Palladium And/Or Copper-Mediated Cross-Coupling Reactions Between 1-Alkynes And Vinyl, Aryl, 1-Alkynyl, 1,2-Propadienyl, Propargyl And Allylic Halides Or Related Compounds. A Review, Rossi. R. Carpita, A. Beilina, F. Org. Prep. Proceed. Int., 1995, 27, 129... 

In the Pd-catalyzed cross-coupling reactions of acylzirconocene chlorides with allylic halides and/or acetates (Section 5.4.4.4), the isolation of the expected p,y-unsaturated ketone is hampered by the formation of the a, P-un saturated ketone, which arises from isomerization of the p,y-double bond. This undesirable formation of the unsaturated ketone can be avoided by the use of a Cu(I) catalyst instead of a Pd catalyst [35], Most Cu(I) salts, with the exception of CuBr - SMe2, can be used as efficient catalysts Thus the reactions of acylzirconocene chlorides with allyl compounds (Table 5 8 and Scheme 5 30) or propargyl halides (Table 5.9) in the presence of a catalytic amount (10 mol%) of Cu(I) in DMF or THF are completed within 1 h at 0°C to give ffie acyl--allyl or acyl-allenyl coupled products, respectively, in good yields. ill... 

As shown in the previous sections, a (cr-allenyl)palladium species, which is formed from a propargyl electrophile and a Pd(0) catalyst, reacts with a hard carbon nucleophile in a manner analogous to the Pd-catalyzed cross-coupling reaction to give a substituted allene. The results indicate that the reactivity of the (cj-allenyl)palladium species is similar to that of an alkenylpalladium intermediate. Indeed, it was found that the (cr-allenyl)palladium species reacted with olefins to give vinylallenes, a reaction process that is similar to that of the Heck reaction of alkenyl halides [54]. 

E. Cross-coupling Reactions with Allyl and Propargyl Halides..1283... 

R. Rossi, A. Carpita, F. Beilina, Palladium- and/ or copper-mediated cross-coupling reactions between 1-alkynes and vinyl, aryl, 1-alkynyl, 1,2-propadienyl, propargyl and allylic halides or related compounds A review, Org. Prep. Proced. Int. 1995, 27, 127-160. 

The cross-coupling reaction of organoboron compounds with organic halides or triflates proceeds selectively in the presence of a base, such as sodium or potassium carbonate, phosphate, hydroxide, and alkoxide [11, 45], The bases can be used in aqueous solution, or in suspension in dioxane or DMF. In contrast, the cross-coupling reaction with certain electrophiles, such as allylic acetates [45], 1,3-butadiene monoxide [49], and propargyl carbonates [50], occurs under neutral conditions without any assistance from a base. The transmetallation of organoboron compounds with palladium halides under basic or neutral conditions can be considered to involve three routes, 1, 2, and 3 (Schemes 2-18, 2-20, and 2-23, below). 

Cyclization of a-propargyl-/3-ketoesters can be combined with cross-coupling of aryl halides or triflates in an oxypalladation-reductive elimination reaction to yield arylfurylmethanes (Equation 12) <2003X4661 >. 

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