Strategic Trimethylsilyldiazomethane Insertion into pinB–SR Followed by Selective Alkylations

Abstract

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.

Opportune gem‐Silylborylation of Carbonyl Compounds: A Modular and Stereocontrolled Entry to Tetrasubstituted Olefins

“…[5] Severali nteresting gem-silylborylations have been developed by reactiono fv inylic gem-dihalides with Me 2 PhSiÀBpin in the presence of lithiated bases (Scheme1a). In that context, and considering our ongoing research based on metal-free insertions of diazo synthons into sigma non-symmetric BÀB [8] and BÀSb onds, [9] we report here the straightforward insertion of the commercially available (trimethylsilyl)diazomethane into bis(pinacolato)diboron (B 2 pin 2 ). [7] The latter example is of fundamental interest because access to gem-difunctionalization of alkenes represents ad irect method to polysubstituted olefins through stereodivergent approaches.…”

“…[7] The latter example is of fundamental interest because access to gem-difunctionalization of alkenes represents ad irect method to polysubstituted olefins through stereodivergent approaches. In that context, and considering our ongoing research based on metal-free insertions of diazo synthons into sigma non-symmetric BÀB [8] and BÀSb onds, [9] we report here the straightforward insertion of the commercially available (trimethylsilyl)diazomethane into bis(pinacolato)diboron (B 2 pin 2 ). The corresponding multi-sub-stitutedH C(Bpin) 2 (SiMe 3 )i nsertion product can eventually be deprotonated in the presence of lithiated bases to generate borona nd silicon stabilized carbanions, able to add to ac arbonylf unctionality (Scheme 1b).…”

Unveiling the role of boroxines in metal-free carbon–carbon homologations using diazo compounds and boronic acids

“… 27 – 32 These doubly functionalised carbon substrates are of interest, as they may be used to generate sequential or orthogonal functionalization at the same carbon atom. 28 , 29 To date, the homologation with TMSCHN 2 has only been performed in combination with boronic acids to access the TMS-free homologation products. 26 , 33 While several proposed mechanisms have been reported, the role of a boronic acid anhydride (boroxine) intermediate in these reactions remains unclear.…”

Frustrated Lewis Pair Catalyzed S–H Bond Borylation

“…Similarly, the insertion of the diazo Me3SiCHN2 in a B-S bond can lead to H−C(SR)(Bpin)(SiMe3). 9 While many transition-metal catalyzed transformations have been reported to generate B-E (E = O, N, S, P) containing species, 10 it was recently demonstrated by Bertrand et al that many of these reagents can be prepared directly from hydroboranes (B-H) and protic reagents (E-H) in the absence of a catalyst. 11 However, the preparation of B-S containing compounds in good yields is challenging since the uncatalyzed borylation of thiols require heating up at 120 °C for up to 96 h. Therefore, catalysis is a requirement in the preparation of thioboranes 12 which are useful precursors for the synthesis of a large array of sulfur containing bioactive molecules.…”

“…The Michael addition on α,-β unsaturated carbonyl compounds can also be performed using B–N, B–S, B–P, and B–Se reagents. Similarly, the insertion of the diazo Me 3 SiCHN 2 in a B–S bond can lead to H–C­(SR)­(Bpin)­(SiMe 3 ) …”