Copper-Mediated S_N2′ Allyl–Alkyl and Allyl–Boryl Couplings of Vinyl Cyclic Carbonates

A method for the copper-catalyzed borylmethylation and borylation of vinyl cyclic carbonates through an S_N2′ mechanism is reported. These singular reactions involve selective S_N2′ allylic substitutions with concomitant ring opening of the cyclic carbonate and with extrusion of CO₂ and formation of a useful hydroxyl functionality in a single step. The stereoselectivity of the homoallylic borylation and allylic borylation processes can be controlled, and synthetically useful unsaturated (<i>E</i>)-pent-2-ene-1,5-diols and (<i>E</i>)-but-2-ene-1,4-diols are accessed

Understanding α,β-Unsaturated Imine Formation from Amine Additions to α,β-Unsaturated Aldehydes and Ketones: An Analytical and Theoretical Investigation

A combination of <i>in situ</i> IR spectroscopy (ReactIR) and DFT calculations have been used to understand what factors govern the selectivity in the addition of primary amines to α,β-unsaturated aldehydes and ketones, i.e., 1,2- versus 1,4-addition. It has been found that the 1,2-addition products (α,β-unsaturated imines following addition and elimination) usually predominate for most systems. However, exceptions, such as methyl vinyl ketone, selectively give 1,4-addition products. This has been rationalized by DFT calculations that show that major conformational effects are involved, controlled mainly by steric effects of carbonyl substituents, resulting in a model that provides simple and predictable preparation of α,β-unsaturated imines for <i>in situ</i> utilization in synthesis

Strategic Trimethylsilyldiazomethane Insertion into pinB–SR Followed by Selective Alkylations

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

A Selective Transformation of Enals into Chiral γ‑Amino Alcohols

A one-pot synthesis of chiral amino alcohols from α,β-unsaturated aldehydes is reported which circumvents competitive 1,2- versus 1,4-boryl addition, by means of using a sterically hindered amine-derived imine. In addition to the complete chemoselectivity, modification of the Cu(I) catalyst with readily available chiral diphosphines, such as (<i>R</i>)-DM-BINAP, gave the 1,4-boryl addition products with high levels of asymmetric induction

Synthesis of a Naphthodiazaborinine and Its Verification by Planarization with Atomic Force Microscopy

Aiming to study new motifs, potentially active as functional materials, we performed the synthesis of a naphthodiazaborinine (the BN isostere of the phenalenyl anion) that is bonded to a hindered di-ortho-substituted aryl system (9-anthracene). We used atomic force microscopy (AFM) and succeeded in both the verification of the original nonplanar structure of the molecule and the planarization of the skeleton by removing H atoms that cause steric hindrance. This study demonstrated that planarization by atomic manipulation is a possible route for extending molecular identification by AFM to nonplanar molecular systems that are difficult to probe with AFM directly

Influence of Phosphoramidites in Copper-Catalyzed Conjugate Borylation Reaction

Copper­(I) has become the preferred metal to catalyze the β-boration of α,β-unsaturated carbonyl compounds, and now we demonstrate that easily accessible monodentate chiral ligands, such as phosphoramidites and phosphites, can be convenient alternative ligands to induce asymmetry in the enantioselective version of this reaction, particularly in the β-boration of α,β-unsaturated imines

Copper-Catalyzed Borylative Ring Closing C–C Coupling toward Spiro- and Dispiroheterocycles

The synthesis of spiroheterocyclic structures with a pendant methylene boronate substituent has been accomplished to promote further functionalization. A Cu-catalyzed borylative ring closing C–C coupling of an alkenyl halide is the key step toward the synthesis of [<i>m</i>.<i>n</i>]-spirocycles (<i>m</i>,<i>n</i> = 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

Thioboration of α,β-Unsaturated Ketones and Aldehydes toward the Synthesis of β‑Sulfido Carbonyl Compounds

Herein a direct β-sulfido carbonyl compound synthesis by the easy activation of RS−Bpin reagents with α,β-unsaturated ketones and aldehydes is reported. This convenient methodology can be performed at room temperature with no other additives. The key point of this reactivity is based on the Lewis acidic properties of the boryl unit of the RS−Bpin reagent interacting with the CO oxygen. Consequently, the SR unit becomes more nucleophilic and promotes the 1,4- versus the 1,2-addition, as a function of the involved substrate. The thioborated products can be further transformed into β-sulfido carbonyl compounds by addition of MeOH