The Superbase‐Mediated Pairwise Substitution of the 2,2′‐ and 6,6′‐Positions in a Biphenyl Derivative

Abstract

The superbasic mixture of butyllithium and potassium tert‐butoxide is powerful enough to enable the double proton abstraction from one ortho and one ortho′ position of 4,4′‐di‐tert‐butylbiphenyl. In this way, a series of functionalized derivatives becomes readily accessible, among them 4,4′‐di‐tert‐butylbiphenyldiyl‐2,2′‐dicarboxylic acid (2a) and 4,4′‐di‐tert‐butylbiphenyl‐2,2′‐diol (2d). The latter compound can be subjected again to a superbase‐promoted double metalation, thus giving rise to 2,2′,6,6′‐tetrasubstituted biphenyl derivatives. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Synthesis of 9‐Gallafluorenes via Group 12 Metal Biphenylenes

“…2,2′‐Dilithiobiphenyl, 2,2′‐dilithiobiphenyl · 2tmeda, phenylgallium dichloride, 6 , 7 ,and 10 were prepared as described in literature.…”

Confirmation of an Early Postulate: BCB Two‐Electron–Three‐Center Bonding in Organo(hydro)boranes

“…10 Even though the low stability of ( A ) 2 precluded any further characterization, we considered this species a stimulating lead structure in the quest for isolable BC(aryl)B‐bridged molecules. Aiming at the kinetic stabilization of ( A ) 2 , we introduced bulky tert ‐butyl substituents at the phenylene rings and prepared 2,7‐di‐ tert ‐butyl‐9‐bromo‐9‐borafluorene ( 1 ; Scheme )22 from 2,7‐di‐ tert ‐butyl‐9,9‐dimethyl‐9‐silafluorene11 and BBr 3 .…”

Confirmation of an Early Postulate: BCB Two‐Electron–Three‐Center Bonding in Organo(hydro)boranes

“…[9,10] Even though the low stability of (A) 2 precluded any further characterization, we considered this species a stimulating lead structure in the quest for isolable BÀC(aryl)ÀBbridged molecules. Aiming at the kinetic stabilization of (A) 2 , we introduced bulky tert-butyl substituents at the phenylene rings and prepared 2,7-di-tert-butyl-9-bromo-9-borafluorene (1; Scheme 1 b) [22] from 2,7-di-tert-butyl-9,9-dimethyl-9-silafluorene [11] and BBr 3 .…”