Regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles catalyzed by cooperative s-block bimetallics

Hydrophosphinylation of Styrenes Catalysed by Well‐Defined s‐Block Bimetallics

“…This instead supports that it is the insertion of styrene that is the rate-determining step, which is consistent with our previous studies using alkali-metal magnesiates for catalytic hydroelementation and addition reactions. [25][26][27][28][29] The marked alkali-metal effect (K > Na > Li) and donor influence suggests that coordination of the alkene via the π-bond to the soft potassium cation also plays a key step in the reaction mechanism. Based on these observations and literature precedent, [16,21] a proposed catalytic cycle for the hydrophosphinylation of styrenes using potassium magnesiates can be constructed (Figure 3).…”

“…[22,23] These heterobimetallics have been widely used for many stoichiometric transformations, [24] and this has more recently been expanded to catalytic regimes. In particular, they have been employed in several catalytic hydroelementation and addition reactions, [25][26][27][28][29] showing superior catalytic activity when compared to the monometallic components, and in many cases even outperform the heavier group 2 congeners. The use of heterobimetallic s-block catalysts has been explored by Westerhausen for the hydrophosphinylation of isocyanates, [30] but in this case, the activity of the heterobimetallic catalyst was comparable to that of the monometallic calcium catalyst.…”

Assessing Alkali‐Metal Effects in the Structures and Reactivity of Mixed‐Ligand Alkyl/Alkoxide Alkali‐Metal Magnesiates

“…Surprisingly, these studies suggest that [Li 2 MgsBu 4 ] (II) is the active species performing the MgÀ Br exchange, the mixed alkyl/alkoxy magnesiate [LiMgsBu 2 (OR')] (I) species is actually unreactive in this process. [15] Building on this work and inspired by recent studies in s-block bimetallic chemistry which have established the key mediating role played by the alkali-metal in main group heterobimetallic systems with applications in homogeneous catalysis, [16][17][18] organic synthesis [19,20] and small molecule activation processes, [21] here we extend our studies on mixed-alkyl/alkoxide alkali-metal magnesiate chemistry to sodium and potassium. By systematically changing the alkali-metal, we evaluate the constitution of these heterobimetallic systems in both solution and in the solid state and investigate their reactivity towards MgÀ Br exchange reactions using 2-bromoanisole which has been chosen as a model substrate.…”

Highly chemoselective conjugate addition of lithium tetraorganozincates to coumarin derivatives and functionalization with electrophiles

“…3 Higher-order homoleptic lithium manganates have also been found to promote direct Mn-I exchange reactions of aryl iodides, 4 whereas sodium and potassium magnesiates have revealed to act as powerful catalysts in promoting hydroamination processes at room temperature 5 or as effective pre-catalysts for the synthesis of novel 1,5-disubstituted triazoles. 6 On our side, we have recently reported on the first transition metal catalyst-and ligand-free conjugate addition of lithium tetraorganozincates to nitroolefins en route to valuable nitroalkanes in up to 98% yield, while working under mild conditions (0 °C) and a short reaction time (30 min). 7 In light of such results, we wondered whether the enhanced nucleophilicity and the unique chemoselectivity displayed by these higher-order zincates could be extended to other kind of nucleophilic addition reactions, such as those towards -unsaturated carbonyl compounds that are an important class of C-C bond-forming reactions in organic chemistry.…”