BORON-COMPOUNDS .114. TRIMETHYLSILYLATED 1,4-DIBORINANES AND 1,3-DIBOROLANES FORMATION, ISOMER SEPARATION, AND CHARACTERIZATION

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 diethyl-2,5 (6)-bis(trimethylsilyl)-1,4-diborinanes (3a-d) and minor amounts of et hyl-trans-2,5-bis(trimethylsilyl)-1,3-diborolane (4a). The 2,5-ee-(Me3 Si)2 compound 3d is isolated as the adduct 3d(Pic)2 (X-ray structure a nalysis), from which pure 3d is obtained with Et2O-BF3. 3d and Me3P fo rm 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 gi ve 6-10, and Me3SiC=CSiMe3 (C) reacts with (Et2BH)2 to form the ring c ompounds 12 and 13 via the presumably threo/erythro mixture of 11a and b.