BORON COMPOUNDS .108. ORGANOSUBSTITUTED CIS-1,2-DIBORYLALKENES AS ELECTROPHILIC CHELATES

Triethylborane (1), 9-ethyl-9-borabicyclo[3.3.1]nonane (9-ethyl-9-BBN) (2), and the cis-1,2-diborylalkenes (Z)-R2BC(R') = C(Et)BEt2 [3: R = Et, R' = Me; 4: R,R' = Et; 5: R = Et, R' = Ph; & R2 = C8H14, R' = Et; 7: R = Ph, R' = Et] react with alkali metal salts MX [M = Na, K; X = H, OMe, OtBu, OSiMe3, OSiEt3] in toluene to give the borates MX-1, MX-2, and the cyclic cis-1,2-diborates M[X((R2)BC(R') = C(Et)BEt2], resp., [e.g. KH-3 to KH-7; NaOMe-4 to NaOMe-6; KOtBu-4, KOSiMe3-4, KOSiEt3-4] with BHB- and B(OR)B-bridges (IR, Multi NMR). Reaction of 1, 2, and 3 - 6 with KCN leads to the monoborates KCN-1, KCN-2, and to the acyclic cis-1,2-diborates KCN-3 to KCN-7. - The cis-2-Boryl-1-silylalkenes (E)-Me3SiC(R') = C(Et)BEt2 [8: R' = Me; 9: R' = Et] and KX [X = H, CN, OMe] form the acyclic borates K[Me3SiC(R') = C(Et)-BEt2X]. The cyclic salts KOtBu-4 and KOSiEt3-4 undergo a B-substituent exchange to the acyclic cis-1,2-diborates K[Et3BC(Et) = C(Et)B(Et)OR] (K-10: R = tBu; K-11: R = OSiEt3).