Premium
Bipyridinium and Phenanthrolinium Dications for Metal‐Free Hydrodefluorination: Distinctive Carbon‐Based Reactivity
Author(s) -
Burton Katherine I.,
Elser Iris,
Waked Alexander E.,
Wagener Tobias,
Andrews Ryan J.,
Glorius Frank,
Stephan Douglas W.
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202101534
Subject(s) - chemistry , hydride , lewis acids and bases , reactivity (psychology) , medicinal chemistry , carbocation , delocalized electron , aryl , stereochemistry , alkyl , catalysis , metal , organic chemistry , medicine , alternative medicine , pathology
Abstract The development of novel Lewis acids derived from bipyridinium and phenanthrolinium dications is reported. Calculations of Hydride Ion Affinity (HIA) values indicate high carbon‐based Lewis acidity at the ortho and para positions. This arises in part from extensive LUMO delocalization across the aromatic backbones. Species [C 10 H 6 R 2 N 2 CH 2 CH 2 ] 2+ (R=H [1 a] 2+ , Me [1 f] 2+ , t Bu [1 g] 2+ ), and [C 12 H 4 R 4 N 2 CH 2 CH 2 ] 2+ (R=H [2 a] 2+ , Me [2 b] 2+ ) were prepared and evaluated for use in the initiation of hydrodefluorination (HDF) catalysis. Compound [2 a] 2+ proved highly effective towards generating catalytically active silylium cations via Lewis acid‐mediated hydride abstraction from silane. This enabled the HDF of a range of aryl‐ and alkyl‐ substituted sp 3 (C−F) bonds under mild conditions. The protocol was also adapted to effect the deuterodefluorination of cis ‐2,4,6‐(CF 3 ) 3 C 6 H 9 . The dications are shown to act as hydride acceptors with the isolation of neutral species C 16 H 14 N 2 ( 3 a ) and C 16 H 10 Me 4 N 2 ( 3 b ) and monocationic species [C 14 H 13 N 2 ] + ( [4 a] + ) and [C 18 H 21 N 2 ]+ ( [4 b] + ). Experimental and computational data provide further support that the dications are initiators in the generation of silylium cations.