Trimethylsilylierte 1,4‐Diborinane und 1,3‐Diborolane ‐ Bildung, Isomeren‐Trennung und Charakterisierung

Abstract

Trimethylsilylated 1,4‐Diborinanes and 1,3‐Diborolanes – Formation, Isomer Separation, and Characterisation Me3SiCCH (A) reacts with excess (Et2BH)2 via the compounds 1, 1′ and 2, 2′ to yield a mixture of four regio‐ and stereoisomeric 1,4‐diethyl‐2,5(6)‐bis(trimethylsilyl)‐1,4‐diborinanes (3a–d) and minor amounts of 1,3‐diethyl‐2‐methyltrans‐2,5‐bis(trimethylsilyl)‐1,3‐diborolane (4a). The 2,5‐ee‐(Me3Si)2 compound 3d is isolated as the adduct 3d(Pic)2 (X‐ray structure analysis), from which pure 3d is obtained with Et2O‐BF3. 3d and Me3P form equilibria of the 1:1 and 1:2 addition compounds 3d(Me3P)n (n = 1,2) at room temperature. Me3SiCCMe (B) reacts with (Et2BH)2 via 5 to give 6–10, and Me3SiCCSiMe3 (C) reacts with (Et2BH)2 to form the ring compounds 12 and 13 via the presumably threo/erythro mixture of 11a and b.

Trithia-diborinane and Bis(bridging-boryl) Complexes of Ruthenium Derived from a [BH3(SCHS)]− Ion

“…Recently, Braunschweig et al reported bis­(cAAC)-stabilized 3,6-dicyano-1,2,4,5-tetrasulfa-3,6-diborinane where the central {B 2 S 4 } ring displays boat conformation and this was the first example of structurally and NMR-spectroscopically characterized {B 2 S 4 }-heterocycle . Selected examples of the structurally characterized diborinane derivatives are listed in Table , and it is clear that the tetra-coordinated boron atoms in the diborinane species are more shielded and appear in the upfield region as compared to the tricoordinated boron atoms. − …”

“…Enormous growth has been observed in the field of boron-containing ring compounds. − The attention was mainly focused on the classes of the borole and boralane rings. , In contrast, the diborinane species and their chemistry with metal complexes remain as a sparsely explored area mainly due to the lack of proper synthetic routes. Although handful of heterocyclic borane compounds are reported, very few diborinane compounds, mainly derivatives, are known to date. − ,− Although some examples of the trithia-diborinane compounds have been reported, there have been no reports on metal complexes of trithia-diborinane species. Compound 2 is the first example of a trithia-diborinane stabilized ruthenium complex.…”

“…The sixmembered ring containing the {CB 2 S 3 } moiety adopts a chair conformation similar to that of the reported diborinane species, such as bis(γ-picoline)-1,4-diethyl-2,5-bis-(trimethylsilyl)-1,4-diborinane and [BH 2 CH 2 SMe] 2 . 10,11 It is unlike that of other substituted diborinanes, such as [(BNMe 2 )(CH 2 )(N−Ar)] 2 (Ar = mesityl, Dip and Xyl), where the central six-membered ring adopts a boat conformation. 12 Meller et al reported the first transitionmetal−diborinane adduct in 1986, [(BMe) 2 (NH){N-(SiMe 3 )} 2 (S){W(CO) 5 }].…”

Catalytic C–H Carboxylation of Terminal Alkynes with Carbon Dioxide

“…Traditional syntheses of propiolic acids include the oxidation of propargylic alcohols or aldehyde derivatives, , the insertion of CO 2 into alkynyl–metal species , obtained by deprotonation of alkynes with strong bases such as alkali metal hydrides or organometallic reagents. − …”