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The Phosphinoboration of N ‐Heterocycles
Author(s) -
Geier Stephen J.,
Vogels Christopher M.,
Mellonie Niall R.,
Daley Erika N.,
Decken Andreas,
Doherty Simon,
Westcott Stephen A.
Publication year - 2017
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.201702203
Subject(s) - pyridine , chemistry , intramolecular force , quinoline , adduct , medicinal chemistry , nucleophile , nitrogen atom , stereochemistry , dimer , ring (chemistry) , organic chemistry , catalysis
The addition of phosphinoboronate ester Ph 2 PBpin (pin=1,2‐O 2 C 2 Me 4 ) ( 1 ) to a number of different N ‐heterocycles has been investigated. Reaction of 1 with pyridine resulted in highly selective formation of the corresponding 1,4‐addition product, with addition of the electron‐deficient Bpin group to the pyridine nitrogen atom and the phosphido group to the para carbon atom. Conversely, reactions of para ‐substituted pyridine derivatives occurred predominately to afford 1,2‐addition products while quinoline reacted to afford the 1,2‐adduct which ultimately isomerized to afford the corresponding 1,4‐addition product. Preliminary computational studies have been undertaken to explore possible pathways for these transformations including transfer of the PPh 2 − anion from [B(PPh 2 ) 2 pin] − to the 4‐position of a borenium/boronium activated pyridine and concerted pathways for 1,2‐addition via intramolecular nucleophilic attack of PPh 2 at C2 of a Ph 2 PBpin‐coordinated pyridine via a four‐centered transition state and intramolecular transfer of PPh 2 to the 2‐position of a boron‐activated pyridine in a phosphido‐bridged dimer involving a six‐centered transition state.