The potassium salts K(bB(R,)CR'=CEthEt,] (A: R = R' = Et; (Etz)C(Et)= (5c) and/or C(Et)BEt B: R2 = C8HI4, R = Me; C: R2 = C8H14, R = Et) react with various electrophiles (H+, R + , Me3E1'"+) to form substituted 1,3,2-diboroxanes (1, is08 b) including 1,2,5-oxadiborolanes (2, 4, 6, 9, lo), dialkylvinylboranes (l'), 2,5-dihydro-1,2,5-oxoniadiboratoles (3, 5) and cis-1,2-diborylalkenes