In the realm of radical chemistry, halogen-atom transfer (XAT) is emerging as a powerful activation strategy in synthetic endeavors to engage otherwise recalcitrant organic halides. Although toxic tin radicals have been in the spotlight as halo-gen abstractors for decades, the era of photocatalysis has brought to light more sustainable options. Herein, we present a comprehensive study on the use of ligated boryl radicals to enable C(sp3)−C(sp3) bond forming reactions via XAT from alkyl halides. Two strategies have been developed using either direct light activation with near UV or photoredox conditions with visible light; both pivoting on N-heterocyclic carbene (NHC) boryl radicals. The present XAT strategy is very mild and accommodates a broad scope of alkyl halides, including medicinally-relevant compounds and biologically-active molecules. The key role of NHC boryl radicals in the operative reaction mechanism has been elucidated through a combination of ex-perimental, spectroscopic and computational studies.

In this paper we report the synthesis of a unique silicon(I)-based metalla-disilirane and report on its reactivity towards TMS-azide and benzophenone. Metal complexes containing disilylenes ((bis)silylenes with a Si‒Si bond) are known, but direct ligation of the Si(I) centers to transition metals has thus far always resulted in formation of multinuclear species. To overcome this problem, we targeted the formation of a mononuclear iron(0)-silicon(I)-based disilylene complex via templated synthesis, starting with ligation of a Si(II)- source to iron(II), followed by a two-step reduction. The DFT structure of the resulting η2-disilylene-iron complex reveals metal-to-silicon -back donation and a delocalized three-center-two-electron (3c‒2e) aromatic system. The Si(I)‒Si(I) bond displays unusual but well-defined reactivity. With TMS-azide, both the azide adduct and the four-membered nitrene complex could be isolated. Reaction with benzophenone led to selective 1,4-addition into the SiSi bond. This work reveals that selective reactions of Si(I)‒Si(I) bonds are made possible by metal ligation.

In recent years, there has been a growing demand for drug design approaches that incorporate a higher number of sp3-hybridized carbons, necessitating the development of innovative cross-coupling strategies to reliably introduce aliphatic fragments. Here, we present a novel and powerful approach for the light-mediated B-alkyl Suzuki−Miyaura cross-coupling between alkyl boranes and aryl bromides. Alkyl boranes can be easily generated via hydroboration from readily available alkenes, exhibiting excellent regioselectivity and enabling the selective transfer of a diverse range of primary alkyl fragments onto the arene ring. This methodology eliminates the need for expensive catalytic systems and sensitive organometallic compounds, operating efficiently at room temperature within just 30 minutes. Interestingly, our mechanistic studies reveal an unexpected mechanistic scenario that operates through transmetalation rather than alkyl radical formation, setting it apart from established metallaphotoredox protocols. Moreover, we demonstrate the advantageous translation of the present protocol to continuous-flow conditions, enhancing scalability, safety, and overall efficiency of the method. This versatile approach offers significant potential for accelerating drug discovery efforts by enabling the introduction of complex aliphatic fragments in a straightforward and reliable manner.