Solvent plays an important role in the photophysical property of donor-acceptor-based photocatalysts. The solvent-dependent access to E vs Z-allylic amines was achieved via decarboxylative vinylation of amino acids with vinyl...

Transition metal-catalyzed asymmetric multicomponent reactions using organoboron compounds have been utilized extensively for C–B, C–C, and other bond-forming reactions. This feature article highlights the important discoveries in this topic.

Organoboron compounds have found widespread application in everyday organic synthesis. The Lewis acidic properties, non-toxicity, stability, and easy commercial availability of organoboron compounds have resulted in considerable attention from organic chemists. Over the last several decades, there has been a sizeable development of new organoboron compounds useful in organic synthesis. Allenylboron compounds have emerged as a promising scaffold for various synthetic transformations, including allenylation and propargylation of carbonyl compounds, imines, activated olefins, and others; hydroboration-allylation with carbonyl/imine, and more. On the other hand, a good number of synthetic methods have evolved over the years to access substituted allenylboron compounds in good yield. This review highlights the methods known to date for the synthesis and reactivity of allenylboron compounds in a chronological manner.

The synthesis of a diverse range of heterobiaryls has been achieved by a transition‐metal‐free sp2–sp2 cross‐coupling strategy using lithiated heterocycle, aryl or heteroaryl boronic ester and an electrophilic halogen source. The construction of heterobiaryls was carried out through electrophilic activation of the aryl–heteroaryl boronate complex, which triggered 1,2‐migration from boron to the carbon atom. Subsequent oxidation of the intermediate boronic ester afforded heterobiaryls in good yield. A comprehensive 11B NMR study has been conducted to support the mechanism. The cross coupling between two nucleophilic cross coupling partners without transition metals reveals a reliable manifold to procure heterobiaryls in good yields. Various heterocycles like furan, thiophene, benzofuran, benzothiophene, and indole are well tolerated. Finally, we have successfully demonstrated the gram scale synthesis of the intermediates for an anticancer drug and OLED material using our methodology.

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Gem-diborylalkanes are an important class of organoboron compounds as they function as a key building block in organic synthesis. In the last decade, there has been a growing interest in...

Stereoselective Zweifel olefination using boronate complexes carrying two different reactive π‐systems was achieved to synthesize vinyl heteroarenes and conjugated 1,3‐dienes in good yield and up to 100% stereoselectivity, which remains unexplored until now. Most importantly, we report the unprecedented formation of E vs. Z‐vinyl heteroarenes for different heteroarenes under identical conditions. Density functional theory (DFT) investigations unveil the mechanistic dichotomy between olefin and heteroarene activation followed by 1,2‐migration, leading to E or Z‐vinyl heteroarenes respectively. We also report a previously unknown reversal of stereoselectivity by using 2,3‐Dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) as an electrophile. The Zweifel olefination using a boronate complex that carries two different olefins was previously unexplored due to significant challenges associated with the site‐selective activation of olefins. We have solved this problem and reported the site‐selective activation of olefins for the stereoselective synthesis of 1,3‐dienes.

The construction of heterobiaryls was carried out without transition metal through electrophilic activation of the aryl–heteroaryl boronate complex using N‐bromosuccinimide (NBS), which triggered 1,2‐migration from boron to the carbon atom. Subsequent oxidation of the intermediate boronic ester afforded heterobiaryls in good yield. Various heterocycles like furan, thiophene, benzofuran, benzothiophene, and indole are well tolerated. For more information see the Communication by S. Panda et al. on page 1922 ff.