Catalytic reduction of carboxylic acids and derivatives all the way to their corresponding methyl‐compounds is very rare and still challenging for homogeneous transition‐metal catalysis. Herein, we report an unprecedented and general catalytic exhaustive reduction of carboxylic functional group straightforwardly to a methyl group. This reaction was achieved using earth‐abundant and readily available titanium as a catalyst. Our system has broad functional group tolerance and works for various other types of oxo‐chemicals such as alcohols, aldehydes, ketones, lactones, and carboxylates (>100 examples). Preliminary mechanistic studies revealed that the in situ‐generated TiIII−H species was vital for this transformation.

Functional group exchanges based on single-bond transformation are rare and challenging. In this regard, functional group exchange reactions of hydrosilanes proved to be more problematic. This is because this exchange requires the cleavage of the C–Si bond, while the Si–H bond is relatively easily activated for hydrosilanes. Herein, we report the first Si–B functional group exchange reactions of hydrosilanes with hydroboranes simply enabled by BH3 as a catalyst. Our methodology works for various aryl and alkyl hydrosilanes and different hydroboranes with the tolerance of general functional groups (up to 115 examples). Control experiments and density functional theory (DFT) studies reveal a distinct reaction pathway that involves consecutive C–Si/B–H and C–B/B–H σ-bond metathesis. Further investigations of using more readily available chlorosilanes, siloxane, fluorosilane, and silylborane for Si–B functional group exchanges, Ge–B functional group exchanges, and depolymerizative Si–B exchanges of polysilanes are also demonstrated. Moreover, the regeneration of MeSiH3 from polymethylhydrosiloxane (PMHS) is achieved. Notably, the formal hydrosilylation of a wide range of alkenes with SiH4 and MeSiH3 to selectively produce (chiral)­trihydrosilanes and (methyl)­dihydrosilanes is realized using inexpensive and readily available PhSiH3 and PhSiH2Me as gaseous SiH4 and MeSiH3 surrogates.

Hydrodehalogenation is a straightforward approach to detoxifying harmful organohalides, in which the halogen atom is formally substituted with a hydrogen atom. Herein, a catalytic system using Cp2TiCl2 as the catalyst and ammonia–borane as the reductant is described. A series of benzyl halides and inactivated alkyl halides (including alkyl chlorides) readily reacted to give the corresponding hydrodehalogenated products in yields of up to 97% (43 examples).