Gem‐diborylalkenes have emerged as efficient reagents for selective cross‐coupling reactions, reduction approaches and Michael additions. The synthesis of 1,1‐diborylalkenes involves condensation of polyborated compounds with aldehydes or ketones followed by B–O elimination, geminal diboration of 1,1‐dihaloalkenes, 1‐haloalkenes or terminal alkynes, dehydrogenative borylation of alkenes, borylation of alkynylboronates and hydroboration of alkynylboronates. These new sets of reactions are general for a wide range of substrates and they can be understood to have complementary mechanisms.

The synthesis of spiroheterocyclic structures with a pendant methylene boronate substituent has been accomplished to promote further functionalization. A Cucatalyzed borylative ring closing C−C coupling of an alkenyl halide is the key step toward the synthesis of [m.n]-spirocycles (m,n = 3−5). Computational studies on the mechanism reproduced all the experimental trends and explain the enhanced reactivity of systems leading to strained smaller rings. The optimized protocol also gives access to dispirocycle scaffolds, fully characterized by X-ray diffraction.

The insertion of the diazo derivative Me3SiCHN2 into pinB-SR σ bonds (R = Ph, Tol, Bn) allows a direct synthesis of multisubstituted H-C(SR)(Bpin)(SiMe3) compounds. Consecutive base-assisted transformations of HC(S)(B) (Si) systems lead to deborylative alkylations, Sommelet-Haüser rearrangements, and deprotoalkylations. Intramolecular cyclizations can be selectively performed either via desilylative or deborylative manifolds by fine-tuning the base employed.

O-GlcNAcylation is a post-translational modification of tau understood to lower the speed and yield of its aggregation, a pathological hallmark of Alzheimer’s disease (AD). O-GlcNAcase (OGA) is the only enzyme that removes O-linked N-acetyl-d-glucosamine (O-GlcNAc) from target proteins. Therefore, inhibition of OGA represents a potential approach for the treatment of AD by preserving the O-GlcNAcylated tau protein. Herein, we report the multifactorial optimization of high-throughput screening hit 8 to a potent, metabolically stable, and orally bioavailable diazaspirononane OGA inhibitor (+)-56. The human OGA X-ray crystal structure has been recently solved, but bacterial hydrolases are still widely used as structural homologues. For the first time, we reveal how a nonsaccharide series of inhibitors binds bacterial OGA and discuss the suitability of two different bacterial orthologues as surrogates for human OGA. These breakthroughs enabled structure–activity relationships to be understood and provided context and boundaries for the optimization of druglike properties.

Copper(i) catalyzes the borylative cyclization of γ-alkenyl aldehydes through chemo- and regioselective addition of Cu–B to CC and concomitant intramolecular 1,2-addition of Cu–C on CO.