✍ Scribed by Köster, Roland ;Seidel, Günter ;Boese, Roland
No coin nor oath required. For personal study only.
Ethyl‐substituted 2,5‐Dihydro‐1,2,5‐oxadiboroles^[1]^
Four N‐Lewis base‐(1,2,5‐oxadiboroles) rac‐5(Do) [Do = ammonia (NH~3~), quinuclidine (Q), pyridine (Py), γ‐picoline (γPic)] of·B(Et)OB(Et)C(Et)=C(Et) (5, identical with II) are prepared by reaction of cis‐Et~2~BC(Et)=C(Et)BEt~2~ (A) with KNH~2~ via the tetraethyl‐substituted (BNBC=C) heterocycles 1‐4.·B(Et)N(SiMe~3~)B(Et)C(Et)=C(Et) (4) reacts with water with elimination of Me~3~SiOH to give rac‐5(NH~3~). The latter undergoes exchange reactions with various N‐bases (Py, γPic, Q) quantitatively forming the 1:1 addition compounds rac‐5(Do) [Do = γPic (X‐ray structure analysis)]. rac‐5(NH~3~) reacts with Ph~3~B to yield H~3~N‐BPh~3~ and the unstable compound 5, which dimerises to (5)~2~ and/or reacts with (EtBO) elimination to afford the boroxin (EtBO)~3~ and, presumably, the nido‐carborane Et~4~C~4~B~2~Et~2~ (6). ‐ The potassium salt·K[B(Et~2~)OB(Et)C(Et) = C(Et)] (B) is transformed with ClPbMe~3~ to EtPbMe~3~ and presumably 5 or to the rearranged heterocycle·B(Et)OB(Et)C(Et~2~)C(Et, PbMe~3~) (7).
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