s-Block Metal Catalysts for the Hydroboration of Unsaturated Bonds

Abstract

The addition of a B–H bond to an unsaturated bond (polarized or unpolarized) is a powerful and atom-economic tool for the synthesis of organoboranes. In recent years, s-block organometallics have appeared as alternative catalysts to transition-metal complexes, which traditionally catalyze the hydroboration of unsaturated bonds. Because of the recent and rapid development in the field of hydroboration of unsaturated bonds catalyzed by alkali (Li, Na, K) and alkaline earth (Mg, Ca, Sr, Ba) metals, we provide a detailed and updated comprehensive review that covers the synthesis, reactivity, and application of s-block metal catalysts in the hydroboration of polarized as well as unsaturated carbon–carbon bonds. Moreover, we describe the main reaction mechanisms, providing valuable insight into the reactivity of the s-block metal catalysts. Finally, we compare these s-block metal complexes with other redox-neutral catalytic systems based on p-block metals including aluminum complexes and f-block metal complexes of lanthanides and early actinides. In this review, we aim to provide a comprehensive, authoritative, and critical assessment of the state of the art within this highly interesting research area.

Visible-light-driven PhSSPh-catalysed regioselective hydroborylation of α,β-unsaturated carbonyl compounds with NHC-boranes

“…Since the first exploration of direct hydroboration of alkenes by Brown in 1956, 6 it has become one of the most powerful tools for forging C–B bonds. 7 Over the past few decades, remarkable efforts have been made in hydroboration reactions that are catalysed by transition metals 8 or visible-light, 9 which are widely used in organic synthesis due to their high catalytic efficiency, high regioselectivity and superior atom economy. Among them, visible-light mediated hydroboration reactions of alkenes with NHC-boranes for preparing α-boryl carbonyl compounds have received increasing attention.…”

Transition Metal‐Free Catalytic C−H Silylation of Terminal Alkynes with bis(Trimethylsilyl)acetylene Initiated by KHMDS

“…In contrast, the concept of using silylacetylenes as an atypical coupling partner has occasionally been deployed and these strategies are not without their own disadvantage, including the use of fluoride reagents or/and expensive crown ethers, harsh conditions, lower chemoselectivity (e. g., the dimerization of phenylacetylenes) and narrow substrate scope. [22][23][24][25] Sustainable and eco-friendly synthetic approaches proceeded by the main-group catalysis have gained recent significant attention, [26][27][28][29][30][31][32][33][34][35][36] especially due to the fact of the high abundance of such catalytic species. This in turn, in combination with scientifically important CÀ H and XÀ H/C bond activations (where X = Si, B, Ge, etc.)…”

“…Sustainable and eco‐friendly synthetic approaches proceeded by the main‐group catalysis have gained recent significant attention, [26–36] especially due to the fact of the high abundance of such catalytic species. This in turn, in combination with scientifically important C−H and X−H/C bond activations (where X=Si, B, Ge, etc.)…”

Silicon–nitrogen bond formation via dealkynative coupling of amines with bis(trimethylsilyl)acetylene mediated by KHMDS

“…Sustainable and eco-friendly synthetic approaches proceeded by the main-group catalysis have gained recent significant attention. [39][40][41][42][43][44] On the basis of our recent success in activating silylacetylenes under sustainable catalysis, [45][46][47][48] we reasoned that an appropriate catalytic manifold could provide an efficient platform to generate diversified libraries of trimethylsilylated amines. In this communication, we report on the catalytic silylation of primary amines with bis(trimethylsilyl)acetylene (BTMSA) for the construction of N-Si bonds via dealkynative coupling, by using potassium bis(trimethylsilylamide) as the catalyst (Figure 1, f).…”