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

Trimethylsilylated 1,4‐Diborinanes and 1,3‐Diborolanes – Formation, Isomer Separation, and Characterisation Me 3 SiCCH (A) reacts with excess (Et 2 BH) 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 ‐(Me 3 Si) 2 compound 3d is isolated as the adduct 3d (Pic) 2 (X‐ray structure analysis), from which pure 3d is obtained with Et 2 O‐BF 3 . 3d and Me 3 P form equilibria of the 1:1 and 1:2 addition compounds 3d (Me 3 P) n ( n = 1,2) at room temperature. Me 3 SiCCMe ( B ) reacts with (Et 2 BH) 2 via 5 to give 6–10 , and Me 3 SiCCSiMe 3 ( C ) reacts with (Et 2 BH) 2 to form the ring compounds 12 and 13 via the presumably threo / erythro mixture of 11a and b.