Recent advances in transition metal-free catalytic hydroelementation (E = B, Si, Ge, and Sn) of alkynes

Abstract

This review describes the recent advances in the transition metal-free hydroelementation of alkynes with various metalloid hydrides.

Overview of Regioselective and Stereoselective Catalytic Hydroboration of Alkynes

“…Although a few previously published reviews summarize the hydroboration of unsaturated compounds, none of them dealt with selective alkyne hydroboration to provide a synthetically useful compound alkenylboron compounds. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Few review reports are also available which summarize the hydroelementation of olefins with specific catalysts [7,14,16,[18][19][20]22,24] or specific substrates, [12] however, the reviews are too limited to a certain subject and touch very small area of monoselective hydroboration of alkynes. Based on our observations, over the past few decades, regio-and stereoselective overview of alkyne hydroboration is a much-discussed topic.…”

Cobalt-Catalyzed Hydroboration of Terminal and Internal Alkynes

“…In addition, one unique advantage of organoboronic acid derivatives over other organometallic nucleophiles is their stability since most of them can be isolated, purified, and stored under air. As a consequence, several methodologies for the synthesis of alkenylboronates have been described. , Among them, transition-metal-catalyzed hydroboration of easily available alkynes represents a straightforward strategy. In this area, although precious transition metals have played an important role, their high cost, low abundance, and environmental issues have lately promoted the use of more earth-abundant and sustainable base-metal catalysts .…”

Aluminum Amidinates: Insights into Alkyne Hydroboration

“…Areas where such main-group systems have shown promise include catalytic dehydrocoupling, hydroamination, hydroboration, and hydrosilylation reactions, as well as examples of stoichiometric oxidative addition and reductive eliminations. 1 − 5 Hydroboration reactions are of particular interest as organoborane compounds are widely exploited as synthetic intermediates, owing to their versatility in a range of carbon–carbon and carbon–heteroatom bond formation reactions. 6 Over the past decade, main-group systems have been shown to efficiently catalyze a host of hydroboration reactions.…”

“…Main-group compounds have been widely shown to mimic transition metal behavior and, as they usually react via different mechanistic pathways, can offer divergent reactivity. Areas where such main-group systems have shown promise include catalytic dehydrocoupling, hydroamination, hydroboration, and hydrosilylation reactions, as well as examples of stoichiometric oxidative addition and reductive eliminations. − Hydroboration reactions are of particular interest as organoborane compounds are widely exploited as synthetic intermediates, owing to their versatility in a range of carbon–carbon and carbon–heteroatom bond formation reactions . Over the past decade, main-group systems have been shown to efficiently catalyze a host of hydroboration reactions. ,− The first example of aluminum-mediated hydroboration dates back to 2000, where a combination of LiAlH 4 , 1,1′-bi-2-naphthol (BINOL), and methanol was found to stoichiometrically reduce acetophenone with HBcat .…”