Tailored Palladium Catalysts for Selective Synthesis of Conjugated Enynes by Monocarbonylation of 1,3‐Diynes

Abstract

For the first time, the monoalkoxycarbonylation of easily available 1,3-diynes to give synthetically useful conjugated enynes has been realized. Key to success was the design and utilization of the new ligand 2,2'-bis(tert-butyl(pyridin-2yl)phosphanyl)-1,1'-binaphthalene (Neolephos), which permits the palladium-catalyzed selective carbonylation under mild conditions, providing a general preparation of functionalized 1,3-enynes in good-to-high yields with excellent chemoselectivities. Synthetic applications that showcase the possibilities of this novel methodology include an efficient one-pot synthesis of 4-aryl-4H-pyrans as well as the rapid construction of various heterocyclic, bicyclic, and polycyclic compounds.

Tuning the Selectivity of Palladium Catalysts for Hydroformylation and Semihydrogenation of Alkynes: Experimental and Mechanistic Studies

“…Recently, we introduced a series of bidentate phosphine ligands by incorporating 2-pyridyl substituents as a built-in base on the phosphorus atoms . By applying some of them in Pd-catalyzed alkoxycarbonylation of alkenes, dienes, and alkynes, a significant improvement in reactivity was achieved.…”

A General and Highly Selective Palladium‐Catalyzed Hydroamidation of 1,3‐Diynes

“…In addition, the corresponding acid, which is generated via hydroxycarbonylation, was isolated as a side product in 16 %. It should be noted that although ligand L6 showed high chemoselectivity for mono‐alkoxycarbonylation of 1,3‐diynes, it was not the most efficient ligand in Pd‐catalyzed alkoxycarbony‐lation of dienes [15d] or diynes [15e] . Commercially available ligands L7 – L16 , including mono and bidentate phosphine ligands, which are commonly used in other carbonylations, [17] were examined, too; however, in all cases no product was detected under the standard conditions.…”

Catalytic Hydrofunctionalization Reactions of 1,3-Diynes

“…As illustrated in Figure 5, in which different amides containing biologically or pharmaceutically relevant skeletons are shown, the molecular complexity achieved by applying the Beller's hydroaminocarbonylation reaction was very high [47]. It should also be noted at this point that, by combining Neolephos with Pd(OAc) 2 and (+)-10-camphorsulfonic acid (CSA), the group of Beller was also able to develop a wide-scope procedure for the monoalkoxycarbonylation of 1,3-diynes, allowing the access to functionalized 1,3-enynes of type 38 in good yields and with excellent chemoselectivity (Scheme 23) [48].…”