2-Boraindane und 2-(Dialkylamino)1-2-benzoborol-Dianionen

✍ Scribed by Herberich, Gerhard E. ;Eigendorf, Uwe ;Englert, Ulli

• Publisher: Wiley (John Wiley & Sons)
• Year: 1993
• Tongue: English
• Weight: 673 KB
• Volume: 126
• Category: Article
• ISSN: 0009-2940
• DOI: 10.1002/cber.19931260618

✦ Synopsis

2‐Boraindanes and 2‐(Dialkylamino)1‐2‐benzoborole Dianions

__ortho__1‐Xylene reacts with the Lochmann‐Schlosser base to produce a mixture of the potassium derivatives K~2~[1,2‐C~6~H~4~(CH~2~)~2~] (2) and K[2‐MeC~6~H~4~CH~2~] (3). Condensation of 1 + 2 with BCl~2~(NR~2~) (RMe, Et, __i__Pr) affords 2‐(dialkylamino)1‐2‐boraindanes (1a–c) (50%). Treatment of 1a, b with LiTMP/TMEDA in THF yields dilithio derivatives [Li(tmeda)]~2~[C~6~H~4~(CH)~2~BNR~2~] (8a, b) (40%) which show tripledecked structures consisting of an aromatic 10′‐electron 2‐benzoborole dianion and two [Li‐(tmeda)]^+^ units facially bound to the borole ring. 1a reacts with HCl/Et~2~O/hexane to give C~6~H~4~(CH~2~)~2~BCl · OEt~2~ (1d · OEt~2~) (76%) which decomposes in vacuo to give the chloro derivative 1d. The methyl derivative C~6~H~4~(CH~2~)~2~BMe (1e) is obtained from 1a by treatment with LiMe/Et~2~O at –78°C and subsequently with HCl/Et~2~O at –78°C (41%). 1a, b react with MeOH at –78°C to give solid adducts C~6~H~4~(CH~2~)~2~BOMe · NHR~2~ (12a, b) while 1c affords C~6~H~4~(CH~2~)~2~BOMe (1f). Subsequent ring‐opening produces 2‐MeC~6~H~4~CH~2~B(OMe)~2~ (13). With the exception of 1b the 2‐boraindanes 1 are crystalline solids. The silylation of the 2‐benzoborole dianions and various (2‐methylbenzyl)borane derivatives is also described.