Fe(OTf)₃-Catalyzed Addition of sp C−H Bonds to Olefins

Abstract

We have developed a novel acid-catalyzed addition of acetylenes to olefins in the presence of catalytic triflic acid or its metal salts. Among the various triflates, the catalytic activities depend on the cation and decrease in the order Fe(3+) > Al(3+) >> H(+), In(3+), Sc(3+) >> Cu(2+), Ag(+). In general, "hard" acids gave higher yields than "soft" acids such as copper and silver triflates. Among relatively hard acids, Fe(OTf)(3) was the best catalyst, which is also the case for ester formation from carboxylic acids and olefins. Our procedure is unique and attractive for the following reasons: (i) The reaction proceeds even for isolated C=C double bonds, as in norbornene. (ii) The reaction is promoted by acid catalysts and does not include an oxidation-reduction cycle for transition metals. (iii) Moreover, these catalysts are inexpensive, abundant, and less toxic than precious-metal-based catalysts. The reaction proceeds even under air and does not require precious metals.

Stereoselective Single (Copper) or Double (Platinum) Boronation of Alkynes Catalyzed by Magnesia‐Supported Copper Oxide or Platinum Nanoparticles

“…Therefore we performed the reaction of phenylacetylene (1) with diboronate 2 in the presence of a series of supported metal nanoparticles with different metals and supports. The results are given in Table 1 (see entries [9][10][11][12][13][14][15][16]. It can be seen that gold nanoparticles supported on magnesia, titania, or ceria did not lead to the unsaturated organoboronate.…”

“…Besides noble metal nanoparticles, there is increasing interest in exploiting the catalytic activity of less costly transition metals. [16,17] In this regard, the use of copper catalysts as substitutes for expensive noble metals is of economic importance. In this report we will show the remarkable contrasting catalytic behavior of CuO/MgO and Pt/MgO, on the one hand, and the differences between these two catalysts and other magnesia-supported metal nanoparticles, on the other.…”

Iron‐Catalysed Hydrofunctionalisation of Alkenes and Alkynes

“…[49] The reaction of norbornene (12) and norbornadiene (69) with terminal alkynes 68 gave selectively exo products 70 and 71 in good to excellent yields. Optimal yields were obtained with an excess amount of the alkyne, and al-though the reactions were usually conducted neat, in some cases the addition of solvent was advantageous.…”

Palladium/Copper Complexes Co‐Catalyzed Highly Enantioselective Ring Opening Reaction of Azabenzonorbornadienes with Terminal Alkynes

“…We rationalized that the relatively high stability of the C À N bond in azabenzonorbornadiene 2a and the low nucleophilicity of phenylacetylene (1a) would be responsible for the failure. In order to tackle this problematic issue, a Lewis acid was added as co-catalyst in the reaction for activating the phenylacetylene 1a [14] and/or the azabenzonorbornadiene 2a. [15] To our delight, superior results were obtained.…”